Road vehicles — Diagnostic communication over Controller Area Network (DoCAN) — Part 4: Requirements for emissions-related systems

This document specifies requirements for CAN-based communication systems between the in-vehicle network and the diagnostic link connector of the vehicle. This document does not specify any requirements related to the in-vehicle CAN network architecture. This document specifies the requirements to enable the in-vehicle CAN-based communication systems to establish, maintain, and terminate communication with the devices connected to the diagnostic link connector.

Véhicules routiers — Diagnostic sur gestionnaire de réseau de communication (DoCAN) — Partie 4: Exigences applicables aux systèmes associés aux émissions

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Published
Publication Date
29-Jul-2021
Current Stage
6060 - International Standard published
Start Date
30-Jul-2021
Completion Date
30-Jul-2021
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INTERNATIONAL ISO
STANDARD 15765-4
Fourth edition
2021-07
Road vehicles — Diagnostic
communication over Controller Area
Network (DoCAN) —
Part 4:
Requirements for emissions-related
systems
Véhicules routiers — Diagnostic sur gestionnaire de réseau de
communication (DoCAN) —
Partie 4: Exigences applicables aux systèmes associés aux émissions
Reference number
ISO 15765-4:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 15765-4:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 15765-4:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Abbreviated terms ............................................................................................................................................................................... 3

5 Conventions ............................................................................................................................................................................................................... 4

6 Application ................................................................................................................................................................................................................. 4

6.1 Vehicle communication initialisation sequence ......................................................................................................... 4

6.1.1 OBDonUDS protocol identification .................................................................................................................. 4

6.1.2 OBDonEDS protocol identification ................................................................................................................... 4

6.1.3 Others ........................................................................................................................................................................................ 4

6.2 External test equipment communication initialisation sequence .............................................................. 4

6.3 Bit rate validation procedure ...................................................................................................................................................... 5

6.3.1 bitrateRecord ...................................................................................................................................................................... 5

6.3.2 Bit rate validation ............................................................................................................................................................ 5

6.3.3 External test equipment error detection provisions ........................................................................ 6

6.4 CAN identifier validation procedure .................................................................................................................................... 7

6.4.1 CAN identifier validation procedure OBDonEDS ................................................................................. 7

6.4.2 CAN identifier validation procedure OBDonUDS ................................................................................. 9

6.5 Support of ECUNAME reporting............................................................................................................................................11

7 Application layer (AL) ..................................................................................................................................................................................11

8 Session layer (SL) ..............................................................................................................................................................................................12

9 Transport layer (TL) ......................................................................................................................................................................................12

10 Network layer (NL) ..........................................................................................................................................................................................12

10.1 General ........................................................................................................................................................................................................12

10.2 Parameter definitions ....................................................................................................................................................................12

10.2.1 Timing parameter values .......................................................................................................................................12

10.2.2 Definition of flow control parameter values .........................................................................................13

10.2.3 Maximum number of OBDonUDS or OBDonEDS ECUs ................................................................14

10.3 Addressing formats ..........................................................................................................................................................................15

10.3.1 Normal and normal fixed addressing format .......................................................................................15

10.3.2 Functional addressing ..............................................................................................................................................15

10.3.3 Physical addressing ....................................................................................................................................................15

10.4 CAN identifier requirements ....................................................................................................................................................16

10.4.1 External test equipment .........................................................................................................................................16

10.4.2 OBDonUDS or OBDonEDS server/ECU ......................................................................................................16

10.5 Mapping of diagnostic addresses .........................................................................................................................................16

10.5.1 OBDonUDS/OBDonEDS CAN identifiers ..................................................................................................16

10.5.2 11-bit CAN identifiers ...............................................................................................................................................17

10.5.3 29-bit CAN identifiers ...............................................................................................................................................18

11 Data link layer (DLL) .....................................................................................................................................................................................18

12 Physical layer (PHY) .......................................................................................................................................................................................18

12.1 General ........................................................................................................................................................................................................18

12.2 Bit rates ......................................................................................................................................................................................................19

12.3 CAN bit timing ......................................................................................................................................................................................19

12.3.1 Parameter values ..........................................................................................................................................................19

© ISO 2021 – All rights reserved iii
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ISO 15765-4:2021(E)

12.3.2 Nominal bit rate 250 kbit/s .................................................................................................................................20

12.3.3 Nominal bit rate 500 kbit/s .................................................................................................................................20

12.4 External test equipment ..............................................................................................................................................................21

12.4.1 Electrical parameters ................................................................................................................................................21

12.4.2 Cable parameters ...................................................................... ....................................................................................24

Bibliography .............................................................................................................................................................................................................................25

iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 15765-4:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 31,

Data communication.

This fourth edition cancels and replaces the third edition (ISO 15765-4:2016), which has been

technically revised.
The main changes compared to the previous edition are as follows:
— changed all time-related parameters to t ;
Parameter_Name
— corrected all occurrences of ⊣⫤ P2 and changed to Δt ;
CAN_max P2_CAN_Client_Max
— Clause 6 title has been changed to application;

— subclause 6.1 title has been changed to vehicle communication initialisation sequence;

— subclause 6.2 title has been changed to external test equipment communication initialisation

sequence;
— changed N_As to t and changed timeout value to 33 ms;
N_As
— changed N_Ar to t and changed timeout value to 33 ms;
N_Ar

— added clarification in 10.3.3 regarding the acceptance of physically addressed request messages.

A list of all parts in the ISO 15765 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 15765-4:2021(E)
Introduction

This document has been established in order to define common requirements for vehicle diagnostic

systems implemented on a controller area network (CAN) communication link, as specified in

ISO 11898-1 and ISO 11898-2. Although primarily intended for diagnostic systems, it also meets

requirements from other CAN-based systems needing a network layer protocol.

To achieve this, it is based on the Open Systems Interconnection (OSI) basic reference model specified

in ISO/IEC 7498-1 and ISO/IEC 10731, which structures communication systems into seven layers.

When mapped on this model, the application protocol and lower OSI layers framework requirements

specified/referenced in the ISO 15765 series are structured according to Figure 1.

Figure 1 illustrates a standards-based documentation concept, which consists of the lower OSI layers

framework, which specifies requirements related to the transport layer, network layer, data link layer

and physical layer standards of the OSI layers 4, 3, 2, and 1.
Figure 1 — DoCAN related OSI layers framework
vi © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 15765-4:2021(E)
Road vehicles — Diagnostic communication over
Controller Area Network (DoCAN) —
Part 4:
Requirements for emissions-related systems
1 Scope

This document specifies requirements for CAN-based communication systems between the in-

vehicle network and the diagnostic link connector of the vehicle. This document does not specify

any requirements related to the in-vehicle CAN network architecture. This document specifies the

requirements to enable the in-vehicle CAN-based communication systems to establish, maintain, and

terminate communication with the devices connected to the diagnostic link connector.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC 7498-1, Information technology — Open Systems Interconnection — Basic Reference Model: The

Basic Model

ISO 11898-1, Road vehicles — Controller area network (CAN) — Part 1: Data link layer and physical

signalling

ISO 11898-2, Road vehicles — Controller area network (CAN) — Part 2: High-speed medium access unit

ISO 14229-2, Road vehicles — Unified diagnostic services (UDS) — Part 2: Session layer services

ISO 15031-3, Road vehicles — Communication between vehicle and external equipment for emissions-

related diagnostics — Part 3: Diagnostic connector and related electrical circuits: Specification and use

ISO 15765-2, Road vehicles — Diagnostic communication over Controller Area Network (DoCAN) — Part 2:

Transport protocol and network layer services
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 7498-1, ISO 11898-1,

ISO 11898-2, ISO 15765-2 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
OBDonEDS
on-board diagnostics on emission diagnostic service
[4]

application protocol request and response messages defined in ISO 15031-5/SAE J1979 dedicated to

the diagnostics of emissions-related systems
© ISO 2021 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 15765-4:2021(E)
3.2
OBDonUDS
on-board diagnostics on unified diagnostic service

application protocol request and response messages defined in the ISO 14229 series and in ISO 27145-3

[5]
or SAE J1979-2 dedicated to the diagnostics of emissions-related systems
4 Symbols and abbreviated terms
4.1 Symbols
— empty table cell or feature undefined
B block size
C , C capacitance of AC termination
AC1 AC2
C capacitance between CAN_H and ground potential
CAN_H
C capacitance between CAN_L and ground potential
CAN_L
C capacitance between CAN_H and CAN_L
DIFF
ΔO oscillator frequency tolerance
F consecutive frame
F flow control frame
F first frame
F frame flow status
F single frame
l maximum cable length between diagnostic link connector and external test
CABLE
equipment
R , R resistance of AC termination
AC1 AC2
t bit time
BIT
t receive bit time
BIT_RX
t transmit bit time
BIT_TX
t external test equipment CAN interface propagation delay (without external test
ETE
equipment cable delay)
t external test equipment cable propagation delay (without external test equip-
ETE_CABLE
ment CAN interface delay)
t network layer timeout value (see ISO 15765-2)
N_Ar
t network layer timeout value (see ISO 15765-2)
N_As
t network layer timeout value (see ISO 15765-2)
N_Br
t network layer timeout value (see ISO 15765-2)
N_Bs
2 © ISO 2021 – All rights reserved
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ISO 15765-4:2021(E)
t network layer timeout value (see ISO 15765-2)
N_Cs
t network layer timeout value (see ISO 15765-2)
N_Cr
t client application wait time on server response on CAN
P2_CAN_Client

t timeout value of the client application to receive a response on a request mes-

P2_CAN_Client_Max
sage
t is the performance timing of the server to prepare the response information
P2_CAN_Server
t is the timeout value of the server to respond on a request message
P2_CAN_Server_Max
t nominal sample point position time
t timing segment 1
SEG1
t timing segment 2
SEG2
t resynchronization jump width time
SJW
t synchronization segment time
SYNCSEG
t frame separation time
STmin
t time quantum
4.2 Abbreviated terms
CAN controller area network
CBFF Classical Base Frame Format
DID data identifier
DLC data length code
DoCAN diagnostic communication over CAN
ECU electronic control unit
ECM engine control module
ETE external test equipment
OBD on-board diagnostics
PID parameter identifier
PhaseSeg1 phase segment 1
PhaseSeg2 phase segment 2
PropSeg propagation segment
SA source address
SJW synchronisation jump width
SP nominal sample point
© ISO 2021 – All rights reserved 3
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ISO 15765-4:2021(E)
SyncSeg synchronization segment
TA target address
TCM transmission control module
5 Conventions
This document is based on OSI service conventions as specified in ISO/IEC 10731.
6 Application
6.1 Vehicle communication initialisation sequence
6.1.1 OBDonUDS protocol identification

Vehicles that support OBDonUDS shall have ECUs that reply to the functional request service identifier

22 and DID F810 for protocol identification.
16 16
6.1.2 OBDonEDS protocol identification

Vehicles that support OBDonEDS shall have ECUs that reply to the functional request service identifier

01 and PID 00 for protocol identification.
16 16
6.1.3 Others

Vehicles that do not respond to either request (6.1.1, 6.1.2) do not support OBD diagnostics specified in

this document.
6.2 External test equipment communication initialisation sequence

The external test equipment shall support the initialisation sequence specified in this document.

The purpose of the external test equipment initialisation sequence is to automatically detect whether

the vehicle supports OBDonUDS or OBDonEDS using CAN as the physical layer specified in Clause 12.

Furthermore, the initialisation sequence determines the communication conformance status of vehicles

by analysing their responses as specified in 6.1.1 and 6.1.2.

For each OBDonUDS or OBDonEDS service that requires the determination of “supported” information,

the external test equipment updates its list of expected responding ECUs prior to any data parameter

requests.

The external test equipment initialisation sequence supports single bit rate initialisation (e.g.

500 kbit/s) and multiple bit rate initialisation (e.g. 250 kbit/s and 500 kbit/s) and is separated into the

following tests:
a) 11-bit CAN identifier validation (see 6.4.1 and 6.4.2);
b) 29-bit CAN identifier validation (see 6.4.1 and 6.4.2).

The external test equipment initialisation sequence shall contain provisions for legacy vehicles using

either CAN or a non-CAN protocol on the CAN pins of the ISO 15031-3 diagnostic link connector.

4 © ISO 2021 – All rights reserved
---------------------- Page: 10 ----------------------
ISO 15765-4:2021(E)
6.3 Bit rate validation procedure
6.3.1 bitrateRecord
The parameter “bitrateRecord” contains the bit rates as specified in 12.2.

The bitrateRecord shall be used to specify the type of initialisation to be performed. If the bitrateRecord

parameter contains a single bit rate, then a single bit rate initialisation sequence shall be performed

using the specified single bit rate (e.g. 500 kbit/s). If the bitrateRecord parameter contains multiple bit

rates, then a multiple bit rate initialisation sequence shall be performed including a bit rate detection

procedure as defined in Figure 2.

Figure 2 shall be performed using the specified multiple bit rates (e.g. 250 kbit/s and 500 kbit/s). The

external test equipment shall use the appropriate CAN bit timing parameter values specified in 12.3.

6.3.2 Bit rate validation

If multiple bit rates are specified in the bitrateRecord parameter, the procedure as defined in Figure 2

shall be used to determine the bit rate to be used in communication with the vehicle's emissions-related

system.

The external test equipment shall set up its CAN interface using the first bit rate contained in the

bitrateRecord. It shall use the CAN bit timing parameter values specified for this bit rate (see 6.3).

© ISO 2021 – All rights reserved 5
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ISO 15765-4:2021(E)
Key

Following the CAN interface setup, the external test equipment shall connect to the CAN network and transmit

a functionally addressed request message with service identifier 01 and PID "supported PIDs" using the

OBDonEDS 11-bit functional request CAN identifier as defined in 10.5.2.

NOTE The immediate transmission is needed in order to activate the CAN error frame monitoring, since

initialising the CAN controller at the wrong bit rate without transmitting any data can leave the CAN controller

in a state of generating error frames on the CAN network.

The external test equipment shall check for any CAN error frame. If the request message is successfully

transmitted onto the CAN network, the external test equipment shall indicate a successful transmission and

proceed with the validation of the CAN identifier as specified in 6.4.1.

If an acknowledge (ACK) check error is detected, then the external test equipment shall continue to retry the

transmission of the request message until the t timeout has elapsed.
N_As

If any other CAN error frame occurred, or an acknowledge check error still occurs after the t timeout has

N_As

elapsed, then the external test equipment shall stop CAN communication on the CAN network.

Proceed with sequence according to Figure 3, key 'a'.

The external test equipment shall check whether more bit rates are contained in the bitrateRecord. If the end

of the bitrateRecord is not reached, the external test equipment shall set up its CAN interface using the next

bit rate in the bitrateRecord and restart the bit rate validation at key 'a' in Figure 2. If no further bit rate is

contained in the bitrateRecord, it shall be assumed that the request was not transmitted successfully. This

indicates that the vehicle does not comply with this document.
Figure 2 — Perform bit rate validation
6.3.3 External test equipment error detection provisions

Where the vehicle uses a physical layer different from that specified for OBDonEDS and OBDonUDS

(see Clause 12) or a non-CAN protocol on the CAN pins of the diagnostic link connector, the transmit

procedure, specified in this document, shall guarantee that in all cases, the external test equipment

6 © ISO 2021 – All rights reserved
---------------------- Page: 12 ----------------------
ISO 15765-4:2021(E)

shall detect that the vehicle does not support CAN as specified for OBDonUDS or OBDonEDS and shall

stop the transmission of the request message immediately.

Where the vehicle uses CAN and the physical layer in accordance with Clause 12, the transmit

procedure given as follows shall guarantee that in all cases, the external test equipment shall detect

that it uses the wrong bit rate for the transmission of the request message and shall stop disturbing

the CAN network. Under normal in-vehicle conditions (i.e. no error frames shall occur during in-vehicle

communication when the external test equipment is disconnected), the external test equipment shall

stop communication on the CAN network prior to the situation where the internal error counters of the

OBDonUDS or OBDonEDS ECU(s) reach critical values.

To achieve this, the external test equipment shall implement the following provisions:

— possibility to immediately stop sending during transmission of any CAN frame;

— the CAN interface should be disconnected within 12 µs from reception of a data frame error

signal. The maximum time for the disconnection is 100 µs;

— with the CAN interface disconnected, the external test equipment shall not be able to transmit

dominant bits on the CAN network;
— possibility to immediately detect any CAN error frame on the CAN network.

The second provision implies that the external test equipment cannot solely rely on the usual CAN

controller error handling since it does most likely flag a CAN error frame only after the “bus-off” state

has been reached (refer to ISO 11898-1 for further details).
6.4 CAN identifier validation procedure
6.4.1 CAN identifier validation procedure OBDonEDS

A functionally addressed service identifier 01 and PID 00 request using the OBDonEDS 11-bit

16 16
functional request CAN identifier, as defined in 10.5.2, shall be transmitted.

The response handling procedure shall be used to receive response messages mapped to data frames

in CBFF from the OBDonEDS ECU(s) or to indicate that no response message is received. If OBDonEDS-

related ECUs are detected, this procedure also builds the list of supported ECUs on the OBDonEDS-

conformant vehicle.

The response validation procedure shall be performed as specified in Figure 3, after the 11-bit CAN

identifier request message transmit procedure (see Figure 2) has succeeded (“OK”).

© ISO 2021 – All rights reserved 7
---------------------- Page: 13 ----------------------
ISO 15765-4:2021(E)
Key

If the transmission of the previously transmitted request message was successful (“OK”), the external test

equipment shall start the P application timer and listen for the physical response CAN identifiers

2_CAN_Client
as defined in 10.5.

If the external test equipment determines a t timeout and no response message has been started,

P2_CAN_Client

then the external test equipment has verified that 11-bit or 29-bit CAN identifiers

...

INTERNATIONAL ISO
STANDARD 15765-4
Fourth edition
Road vehicles — Diagnostic
communication over Controller Area
Network (DoCAN) —
Part 4:
Requirements for emissions-related
systems
Véhicules routiers — Diagnostic sur gestionnaire de réseau de
communication (DoCAN) —
Partie 4: Exigences applicables aux systèmes associés aux émissions
PROOF/ÉPREUVE
Reference number
ISO 15765-4:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 15765-4:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 15765-4:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Abbreviated terms ............................................................................................................................................................................... 3

5 Conventions ............................................................................................................................................................................................................... 4

6 Application ................................................................................................................................................................................................................. 4

6.1 Vehicle communication initialisation sequence ......................................................................................................... 4

6.1.1 OBDonUDS protocol identification .................................................................................................................. 4

6.1.2 OBDonEDS protocol identification ................................................................................................................... 4

6.1.3 Others ........................................................................................................................................................................................ 4

6.2 External test equipment communication initialisation sequence .............................................................. 4

6.3 Bit rate validation procedure ...................................................................................................................................................... 5

6.3.1 bitrateRecord ...................................................................................................................................................................... 5

6.3.2 Bit rate validation ............................................................................................................................................................ 5

6.3.3 External test equipment error detection provisions ........................................................................ 6

6.4 CAN identifier validation procedure .................................................................................................................................... 7

6.4.1 CAN identifier validation procedure OBDonEDS ................................................................................. 7

6.4.2 CAN identifier validation procedure OBDonUDS ................................................................................. 9

6.5 Support of ECUNAME reporting............................................................................................................................................11

7 Application layer (AL) ..................................................................................................................................................................................11

8 Session layer (SL) ..............................................................................................................................................................................................12

9 Transport layer (TL) ......................................................................................................................................................................................12

10 Network layer (NL) ..........................................................................................................................................................................................12

10.1 General ........................................................................................................................................................................................................12

10.2 Parameter definitions ....................................................................................................................................................................12

10.2.1 Timing parameter values .......................................................................................................................................12

10.2.2 Definition of flow control parameter values .........................................................................................13

10.2.3 Maximum number of OBDonUDS or OBDonEDS ECUs ................................................................14

10.3 Addressing formats ..........................................................................................................................................................................15

10.3.1 Normal and normal fixed addressing format .......................................................................................15

10.3.2 Functional addressing ..............................................................................................................................................15

10.3.3 Physical addressing ....................................................................................................................................................15

10.4 CAN identifier requirements ....................................................................................................................................................16

10.4.1 External test equipment .........................................................................................................................................16

10.4.2 OBDonUDS or OBDonEDS server/ECU ......................................................................................................16

10.5 Mapping of diagnostic addresses .........................................................................................................................................16

10.5.1 OBDonUDS/OBDonEDS CAN identifiers ..................................................................................................16

10.5.2 11-bit CAN identifiers ...............................................................................................................................................17

10.5.3 29-bit CAN identifiers ...............................................................................................................................................18

11 Data link layer (DLL) .....................................................................................................................................................................................18

12 Physical layer (PHY) .......................................................................................................................................................................................18

12.1 General ........................................................................................................................................................................................................18

12.2 Bit rates ......................................................................................................................................................................................................19

12.3 CAN bit timing ......................................................................................................................................................................................19

12.3.1 Parameter values ..........................................................................................................................................................19

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
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ISO 15765-4:2021(E)

12.3.2 Nominal bit rate 250 kbit/s .................................................................................................................................20

12.3.3 Nominal bit rate 500 kbit/s .................................................................................................................................20

12.4 External test equipment ..............................................................................................................................................................21

12.4.1 Electrical parameters ................................................................................................................................................21

12.4.2 Cable parameters ...................................................................... ....................................................................................24

Bibliography .............................................................................................................................................................................................................................25

iv PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 15765-4:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 31,

Data communication.

This fourth edition cancels and replaces the third edition (ISO 15765-4:2016), which has been

technically revised.
The main changes compared to the previous edition are as follows:
— changed all time-related parameters to t ;
Parameter_Name
— corrected all occurrences of ⊣⫤ P2 and changed to Δt ;
CAN_max P2_CAN_Client_Max
— Clause 6 title has been changed to application;

— subclause 6.1 title has been changed to vehicle communication initialisation sequence;

— subclause 6.2 title has been changed to external test equipment communication initialisation

sequence;
— changed N_As to t and changed timeout value to 33 ms;
N_As
— changed N_Ar to t and changed timeout value to 33 ms;
N_Ar

— added clarification in 10.3.3 regarding the acceptance of physically addressed request messages.

A list of all parts in the ISO 15765 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 15765-4:2021(E)
Introduction

This document has been established in order to define common requirements for vehicle diagnostic

systems implemented on a controller area network (CAN) communication link, as specified in

ISO 11898-1 and ISO 11898-2. Although primarily intended for diagnostic systems, it also meets

requirements from other CAN-based systems needing a network layer protocol.

To achieve this, it is based on the Open Systems Interconnection (OSI) basic reference model specified

in ISO/IEC 7498-1 and ISO/IEC 10731, which structures communication systems into seven layers.

When mapped on this model, the application protocol and lower OSI layers framework requirements

specified/referenced in the ISO 15765 series are structured according to Figure 1.

Figure 1 illustrates a standards-based documentation concept, which consists of the lower OSI layers

framework, which specifies requirements related to the transport layer, network layer, data link layer

and physical layer standards of the OSI layers 4, 3, 2, and 1.
Figure 1 — DoCAN related OSI layers framework
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INTERNATIONAL STANDARD ISO 15765-4:2021(E)
Road vehicles — Diagnostic communication over
Controller Area Network (DoCAN) —
Part 4:
Requirements for emissions-related systems
1 Scope

This document specifies requirements for CAN-based communication systems between the in-

vehicle network and the diagnostic link connector of the vehicle. This document does not specify

any requirements related to the in-vehicle CAN network architecture. This document specifies the

requirements to enable the in-vehicle CAN-based communication systems to establish, maintain, and

terminate communication with the devices connected to the diagnostic link connector.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC 7498-1, Information technology — Open Systems Interconnection — Basic Reference Model: The

Basic Model

ISO 11898-1, Road vehicles — Controller area network (CAN) — Part 1: Data link layer and physical

signalling

ISO 11898-2, Road vehicles — Controller area network (CAN) — Part 2: High-speed medium access unit

ISO 14229-2, Road vehicles — Unified diagnostic services (UDS) — Part 2: Session layer services

ISO 15031-3, Road vehicles — Communication between vehicle and external equipment for emissions-

related diagnostics — Part 3: Diagnostic connector and related electrical circuits: Specification and use

ISO 15765-2, Road vehicles — Diagnostic communication over Controller Area Network (DoCAN) — Part 2:

Transport protocol and network layer services
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 7498-1, ISO 11898-1,

ISO 11898-2, ISO 15765-2 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
OBDonEDS
on-board diagnostics on emission diagnostic service
[4]

application protocol request and response messages defined in ISO 15031-5/SAE J1979 dedicated to

the diagnostics of emissions-related systems
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ISO 15765-4:2021(E)
3.2
OBDonUDS
on-board diagnostics on unified diagnostic service

application protocol request and response messages defined in the ISO 14229 series and in ISO 27145-3

[5]
or SAE J1979-2 dedicated to the diagnostics of emissions-related systems
4 Symbols and abbreviated terms
4.1 Symbols
— empty table cell or feature undefined
B block size
C , C capacitance of AC termination
AC1 AC2
C capacitance between CAN_H and ground potential
CAN_H
C capacitance between CAN_L and ground potential
CAN_L
C capacitance between CAN_H and CAN_L
DIFF
ΔO oscillator frequency tolerance
F consecutive frame
F flow control frame
F first frame
F frame flow status
F single frame
l maximum cable length between diagnostic link connector and external test
CABLE
equipment
R , R resistance of AC termination
AC1 AC2
t bit time
BIT
t receive bit time
BIT_RX
t transmit bit time
BIT_TX
t external test equipment cable propagation delay (without external test equip-
ETE_CABLE
ment CAN interface delay)
t network layer timeout value (see ISO 15765-2)
N_Ar
t network layer timeout value (see ISO 15765-2)
N_As
t network layer timeout value (see ISO 15765-2)
N_Br
t network layer timeout value (see ISO 15765-2)
N_Bs
t network layer timeout value (see ISO 15765-2)
N_Cs
t client application wait time on server response on CAN
P2_CAN_Client
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ISO 15765-4:2021(E)

t timeout value of the client application to receive a response on a request mes-

P2_CAN_Client_Max
sage
t is the performance timing of the server to prepare the response information
P2_CAN_Server
t is the timeout value of the server to respond on a request message
P2_CAN_Server_Max
t nominal sample point position time
t timing segment 1
SEG1
t timing segment 2
SEG2
t resynchronization jump width time
SJW
t synchronization segment time
SYNCSEG
t frame separation time
STmin
t external test equipment CAN interface propagation delay (without external test
ETE
equipment cable delay)
t time quantum
4.2 Abbreviated terms
CAN controller area network
CBFF Classical Base Frame Format
DID data identifier
DLC data length code
DoCAN diagnostic communication over CAN
ECU electronic control unit
ECM engine control module
ETE external test equipment
OBD on-board diagnostics
PID parameter identifier
PhaseSeg1 phase segment 1
PhaseSeg2 phase segment 2
PropSeg propagation segment
SA source address
SJW synchronisation jump width
SP nominal sample point
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ISO 15765-4:2021(E)
SyncSeg synchronization segment
TA target address
TCM transmission control module
5 Conventions
This document is based on OSI service conventions as specified in ISO/IEC 10731.
6 Application
6.1 Vehicle communication initialisation sequence
6.1.1 OBDonUDS protocol identification

Vehicles that support OBDonUDS shall have ECUs that reply to the functional request service identifier

22 and DID F810 for protocol identification.
16 16
6.1.2 OBDonEDS protocol identification

Vehicles that support OBDonEDS shall have ECUs that reply to the functional request service identifier

01 and PID 00 for protocol identification.
16 16
6.1.3 Others

Vehicles that do not respond to either request (6.1.1, 6.1.2) do not support OBD diagnostics specified in

this document.
6.2 External test equipment communication initialisation sequence

The external test equipment shall support the initialisation sequence specified in this document.

The purpose of the external test equipment initialisation sequence is to automatically detect whether

the vehicle supports OBDonUDS or OBDonEDS using CAN as the physical layer specified in Clause 12.

Furthermore, the initialisation sequence determines the communication conformance status of vehicles

by analysing their responses as specified in 6.1.1 and 6.1.2.

For each OBDonUDS or OBDonEDS service that requires the determination of “supported” information,

the external test equipment updates its list of expected responding ECUs prior to any data parameter

requests.

The external test equipment initialisation sequence supports single bit rate initialisation (e.g.

500 kbit/s) and multiple bit rate initialisation (e.g. 250 kbit/s and 500 kbit/s) and is separated into the

following tests:
a) 11-bit CAN identifier validation (see 6.4.1 and 6.4.2);
b) 29-bit CAN identifier validation (see 6.4.1 and 6.4.2).

The external test equipment initialisation sequence shall contain provisions for legacy vehicles using

either CAN or a non-CAN protocol on the CAN pins of the ISO 15031-3 diagnostic link connector.

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ISO 15765-4:2021(E)
6.3 Bit rate validation procedure
6.3.1 bitrateRecord
The parameter “bitrateRecord” contains the bit rates as specified in 12.2.

The bitrateRecord shall be used to specify the type of initialisation to be performed. If the bitrateRecord

parameter contains a single bit rate, then a single bit rate initialisation sequence shall be performed

using the specified single bit rate (e.g. 500 kbit/s). If the bitrateRecord parameter contains multiple bit

rates, then a multiple bit rate initialisation sequence shall be performed including a bit rate detection

procedure as defined in Figure 2.

Figure 2 shall be performed using the specified multiple bit rates (e.g. 250 kbit/s and 500 kbit/s). The

external test equipment shall use the appropriate CAN bit timing parameter values specified in 12.3.

6.3.2 Bit rate validation

If multiple bit rates are specified in the bitrateRecord parameter, the procedure as defined in Figure 2

shall be used to determine the bit rate to be used in communication with the vehicle's emissions-related

system.

The external test equipment shall set up its CAN interface using the first bit rate contained in the

bitrateRecord. It shall use the CAN bit timing parameter values specified for this bit rate (see 6.3).

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ISO 15765-4:2021(E)
Key

Following the CAN interface setup, the external test equipment shall connect to the CAN network and transmit

a functionally addressed request message with service identifier 01 and PID "supported PIDs" using the

OBDonEDS 11-bit functional request CAN identifier as defined in 10.5.2.

NOTE The immediate transmission is needed in order to activate the CAN error frame monitoring, since

initialising the CAN controller at the wrong bit rate without transmitting any data can leave the CAN controller

in a state of generating error frames on the CAN network.

The external test equipment shall check for any CAN error frame. If the request message is successfully

transmitted onto the CAN network, the external test equipment shall indicate a successful transmission and

proceed with the validation of the CAN identifier as specified in 6.4.1.

If an acknowledge (ACK) check error is detected, then the external test equipment shall continue to retry the

transmission of the request message until the t timeout has elapsed.
N_As

If any other CAN error frame occurred, or an acknowledge check error still occurs after the t timeout has

N_As

elapsed, then the external test equipment shall stop CAN communication on the CAN network.

Proceed with sequence according to Figure 3, key 'a'.

The external test equipment shall check whether more bit rates are contained in the bitrateRecord. If the end

of the bitrateRecord is not reached, the external test equipment shall set up its CAN interface using the next

bit rate in the bitrateRecord and restart the bit rate validation at key 'a' in Figure 2. If no further bit rate is

contained in the bitrateRecord, it shall be assumed that the request was not transmitted successfully. This

indicates that the vehicle does not comply with this document.
Figure 2 — Perform bit rate validation
6.3.3 External test equipment error detection provisions

Where the vehicle uses a CAN with a physical layer different from that specified for OBDonEDS and

OBDonUDS (see Clause 12) or a non-CAN protocol on the CAN pins of the diagnostic link connector,

the transmit procedure, specified in this document, shall guarantee that in all cases, the external test

equipment shall detect that the vehicle does not support CAN as specified for OBDonUDS or OBDonEDS

and shall stop the transmission of the request message immediately.
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ISO 15765-4:2021(E)

Where the vehicle uses CAN and the physical layer in accordance with Clause 12, the transmit

procedure given as follows shall guarantee that in all cases, the external test equipment shall detect

that it uses the wrong bit rate for the transmission of the request message and shall stop disturbing

the CAN network. Under normal in-vehicle conditions (i.e. no error frames shall occur during in-vehicle

communication when the external test equipment is disconnected), the external test equipment shall

stop communication on the CAN network prior to the situation where the internal error counters of the

OBDonUDS or OBDonEDS ECU(s) reach critical values.

To achieve this, the external test equipment shall implement the following provisions:

— possibility to immediately stop sending during transmission of any CAN frame;

— the CAN interface should be disconnected within 12 µs from reception of a data frame error

signal. The maximum time for the disconnection is 100 µs;

— with the CAN interface disconnected, the external test equipment shall not be able to transmit

dominant bits on the CAN network;
— possibility to immediately detect any CAN error frame on the CAN network.

The second provision implies that the external test equipment cannot solely rely on the usual CAN

controller error handling since it does most likely flag a CAN error frame only after the “bus-off” state

has been reached (refer to ISO 11898-1 for further details).
6.4 CAN identifier validation procedure
6.4.1 CAN identifier validation procedure OBDonEDS

A functionally addressed service identifier 01 and PID 00 request using the OBDonEDS 11-bit

16 16
functional request CAN identifier, as defined in 10.5.2, shall be transmitted.

The response handling procedure shall be used to receive response messages mapped to data frames

in CBFF from the OBDonEDS ECU(s) or to indicate that no response message is received. If OBDonEDS-

related ECUs are detected, this procedure also builds the list of supported ECUs on the OBDonEDS-

conformant vehicle.

The response validation procedure shall be performed as specified in Figure 3, after the 11-bit CAN

identifier request message transmit procedure (see Figure 2) has succeeded (“OK”).

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ISO 15765-4:2021(E)
Key

If the transmission of the previously transmitted request message was successful (“OK”), the external test

equipment shall start the P application timer and listen for the physical response CAN identifiers

2_CAN_Client
as defined in 10.5.
If the external test equipment determines a t timeout and no response mess
...

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