ISO 27145-4:2012

Road vehicles — Implementation of World-Wide Harmonized On-Board Diagnostics (WWH-OBD) communication requirements — Part 4: Connection between vehicle and test equipment

ISO 27145-4:2012 defines the requirements to successfully establish, maintain and terminate communication with a vehicle that implements the requirements of the World-Wide Harmonized On-Board Diagnostic Global Technical Regulations (Global technical regulation No. 5). This requires plug and play communication capabilities for the vehicle as well as for any test equipment that intends to establish communication with a vehicle. ISO 27145-4:2012 details all the OSI layer requirements to achieve this goal. ISO 27145-4:2012 is intended to become the single communication standard for access to information relating to vehicle on‑board diagnostics (VOBD). To allow for a smooth migration from the existing communication standards to this future world-wide standardized communication standard, the communication concept as specified in ISO 27145-4:2012 is based on two different data links: · Diagnostic communication over Controller Area Network (DoCAN), ISO 15765-4; · Diagnostic communication over Internet Protocol (DoIP), ISO 13400 (all parts). Use cases deriving from country-specific implementation of Global Technical Regulation No. 5 into local legislation are not included in ISO 27145-4:2012.

Véhicules routiers — Mise en application des exigences de communication pour le diagnostic embarqué harmonisé à l'échelle mondiale (WWH-OBD) — Partie 4: Connexion entre véhicule et équipement d'essai

General Information

• Status: Withdrawn
• Publication Date: 13-Aug-2012
• Withdrawal Date: 13-Aug-2012
• ICS: 43.040.10 - Electrical and electronic equipment
• ICS: 43.180 - Diagnostic, maintenance and test equipment
• Technical Committee: ISO/TC 22/SC 31 - Data communication
• Drafting Committee: ISO/TC 22/SC 31/WG 2 - Vehicle diagnostic protocols
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 29-Mar-2016

Relations

• Revised: ISO 27145-4:2016 - Road vehicles — Implementation of World-Wide Harmonized On-Board Diagnostics (WWH-OBD) communication requirements — Part 4: Connection between vehicle and test equipment
• Effective Date: 05-Nov-2015
• Revises: ISO/PAS 27145-4:2006 - Road vehicles — Implementation of WWH-OBD communication requirements — Part 4: Connection between vehicle and test equipment
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 27145-4
First edition
2012-08-15
Road vehicles — Implementation of
World-Wide Harmonized On-Board
Diagnostics (WWH-OBD) communication
requirements —
Part 4:
Connection between vehicle and test
equipment
Véhicules routiers — Mise en application des exigences de
communication pour le diagnostic embarqué harmonisé à l’échelle
mondiale (WWH-OBD) —
Partie 4: Connexion entre véhicule et équipement d’essai
Reference number
ISO 27145-4:2012(E)
©
ISO 2012

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ISO 27145-4:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
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Published in Switzerland
ii © ISO 2012 – All rights reserved

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ISO 27145-4:2012(E)
Contents Page
Foreword .iv
0 Introduction . v
0.1 Overview . v
0.2 SAE document reference concept . v
0.3 SAE digital annex revision procedure . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions . 2
3.2 Abbreviated terms . 2
4 Conventions . 3
5 Document overview . 3
6 Vehicle and external test equipment connection requirements . 4
6.1 Overview . 4
6.2 Data link independent requirements . 5
6.3 Support of only one WWH-OBD-compliant external test equipment at a time . 5
7 Wired CAN connection based on ISO 15765-4 . 5
7.1 Network scenario requirements . 5
7.2 Initialization sequence . 5
7.3 ISO 27145-3 WWH-OBD protocol validation sequence . 5
7.4 Application layer — DoCAN . 5
7.5 Presentation layer . 6
7.6 Session layer . 7
7.7 Transport layer . 7
7.8 Network layer . 8
7.9 Data link layer . 8
7.10 Physical layer . 8
7.11 Diagnostic connector . 8
8 Wired Ethernet connection based on ISO 13400 . 8
8.1 Network scenario requirements . 8
8.2 Initialization sequence . 9
8.3 ISO 27145-3 WWH-OBD protocol validation sequence .12
8.4 Application layer — DoIP .13
8.5 Presentation layer .14
8.6 Session layer .14
8.7 Transport layer .15
8.8 Network layer .16
8.9 Data link layer .16
8.10 Physical layer .16
8.11 Diagnostic connector .16
Bibliography .17
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ISO 27145-4:2012(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 27145-4 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3, Electrical
and electronic equipment.
This first edition of ISO 27145-4 cancels and replaces ISO/PAS 27145-4:2006, which has been technically revised.
ISO 27145 consists of the following parts, under the general title Road vehicles — Implementation of World-
Wide Harmonized On-Board Diagnostics (WWH-OBD) communication requirements:
— Part 1: General information and use case definition
— Part 2: Common data dictionary
— Part 3: Common message dictionary
— Part 4: Connection between vehicle and test equipment
The following parts are under preparation:
— Part 6: External test equipment
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ISO 27145-4:2012(E)
0 Introduction
0.1 Overview
The ISO 27145 series includes the communication between the vehicle’s on-board diagnostics (OBD) systems
and external test equipment within the scope of the World-Wide Harmonized On-Board Diagnostics Global
Technical Regulations (WWH-OBD GTR).
It has been established in order to apply the unified diagnostic services (specified in ISO 14229-1) to
WWH-OBD systems.
The ISO 27145 series includes the communication between the vehicle’s WWH-OBD systems and external
(off-board) “generic” test equipment within the scope of the country-specific regulatory requirements.
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 services specified by ISO 27145 are broken into
— diagnostic services (layer 7), specified in ISO 27145-3 with reference to ISO 14229-1,
— presentation layer (layer 6), specified in ISO 27145-2 with reference to SAE J1930-DA, SAE J1939 Companion
Spreadsheet (SPNs), SAE J1939-73:2010, Appendix A (FMIs), SAE J1979-DA, and SAE J2012-DA,
— session layer services (layer 5), specified in ISO 14229-2,
— transport layer services (layer 4), specified in this part of ISO 27145 with reference to ISO 13400-2,
ISO 15765-2 and ISO 15765-4,
— network layer services (layer 3), specified in this part of ISO 27145 with reference to ISO 15765-4,
ISO 15765-2 and ISO 13400-2,
— data link layer (layer 2), specified in this part of ISO 27145 with reference to ISO 11898-1, ISO 11898-2,
ISO 15765-4, ISO 13400-3 and IEEE 802.3, and
— physical layer (layer 1), specified in this part of ISO 27145 with reference to ISO 11898-1, ISO 11898-2,
ISO 15765-4, ISO 13400-3 and IEEE 802.3,
in accordance with Table 1.
Table 1 — WWH-OBD specification reference applicable to the OSI layers
Applicability OSI 7 layer WWH-OBD document reference
Application (layer 7) ISO 14229-1, ISO 27145-3
Presentation (layer 6) ISO 27145-2,
SAE J1930-DA, SAE J1939 Companion Spreadsheet (SPNs),
SAE J1939-73:2010, Appendix A (FMIs), SAE J1979-DA, SAE J2012-DA
Seven layers
Session (layer 5) ISO 14229-2
according to
ISO/IEC 7498-1 and
Transport (layer 4)
ISO 15765-2 DoCAN, ISO 13400-2 DoIP
ISO/IEC 10731
ISO 15765-4 DoCAN, TCP & IP
Network (layer 3)
ISO 27145-4
Data link (layer 2) ISO 11898-1 CAN DLL,
ISO 13400-3 DoIP,
ISO 11898-2 CAN HS,
Physical (layer 1) IEEE 802.3
ISO 15765-4 DoCAN
0.2 SAE document reference concept
ISO 27145 makes reference to several SAE documents which contain the terms, data and diagnostic trouble
code (DTC) definitions.
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ISO 27145-4:2012(E)
ISO 27145-2 defines a common data dictionary for the ISO 27145 series, according to the definitions in the
following documents (see Figure 1).
— SAE J1930-DA: this digital annex contains all standardized naming objects, terms and abbreviated terms.
— SAE J1939 Companion Spreadsheet and SAE J1939-73: SAE J1939 Companion Spreadsheet indexes
names for suspect parameter numbers (SPNs) that provide an alternative presentation format for
SAE J2012-DA DTCs. SPNs are combined with failure mode indicators (FMIs) to form the full alternative
presentation. FMIs are described in SAE J1939-73:2010, Appendix A.
NOTE The SAE J1939 Companion Spreadsheet is a document which supplements the SAE J1939 family of
standards and contains SPNs and parameter group numbers (PGNs).
— SAE J1979-DA: this digital annex contains all standardized data items such as data identifiers (DIDs), test
identifiers (TIDs), monitor identifiers (MIDs) and infotype identifiers (ITIDs).
— SAE J2012-DA: this digital annex contains all standardized data items such as DTC definitions and FTB
(failure type byte) definitions.
ISO 27145-2
WWH-OBD
common data dictionary
1 2
SAE J1930-DA
SAE J1939
digital annex of
SAE J1939-73:2010
SAE J2012-DA
Companion
SAE J1979-DA electrical /electronic
[Appendix A]
digital annex of
Spreadsheet
digital annex of E/E systems diagnostic
diagnostic trouble
diagnostic test modes terms, definitions,
code definitions
abbreviations and
acronyms
Key
1 SAE digital annexes: data definitions
2 SAE J1939 series of documents: DTC definitions
Figure 1 — SAE digital annex document reference
0.3 SAE digital annex revision procedure
New regulatory requirements drive new in-vehicle technology to lower emissions, improve safety, etc. It is
important to standardize new technology-related OBD monitor data and DTCs in order to support the external
(off-board) “generic” test equipment. All relevant information is proposed by the automotive industry, represented
by members of the appropriate SAE task force.
ISO 27145-2 references a “Change request form” for use with new data items to be defined by the SAE
task force for standardization. It is intended that the standardized data items be defined in SAE J1930-DA,
SAE J1979-DA, SAE J2012-DA and SAE J1939. It is intended that the documents be published on the SAE
store website once the information has been balloted and approved.
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ISO 27145-4:2012(E)
The revision request forms and instructions for updating the registers to ISO 27145 can be obtained on the
following data registration websites:
— For SAE J1930-DA: http://www.sae.org/servlets/works/committeeHome.do?comtID=TEVDS7
The column entitled “Resources” shows a document with the title: J1930-DA_Revision_Request_Form.
doc. Double click on the name to download the document with the filename: “SAE_J1930-DA_Revision_
Request_Form.doc”.
— For SAE J1939: http://www.sae.org/
Search “J1939 Request”, select “J1939 Request Processing Group”, select “J1939 Request Processing
Form and Guidelines”.
— For SAE J1979-DA: http://www.sae.org/servlets/works/committeeHome.do?comtID=TEVDS14
The column entitled “Resources” shows a document with the title: J1979-DA_Revision_Request_Form.
doc. Double click on the name to download the document with the filename: “SAE_J1979-DA_Revision_
Request_Form.doc”.
— For SAE J2012-DA: http://www.sae.org/servlets/works/committeeHome.do?comtID=TEVDS9
The column entitled “Resources” shows a document with the title: J2012-DA_Revision_Request_Form.
doc. Double click on the name to download the document with the filename: “SAE_J2012-DA_Revision_
Request_Form.doc”.
It is intended that the revision request form be filled out with the request.
It is intended that e-mails with completed revision request forms as attachments be sent to:
E-mail: [e-mail]
E-mail: [e-mail]
E-mail: [e-mail]
E-mail: [e-mail]
© ISO 2012 – All rights reserved vii

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INTERNATIONAL STANDARD ISO 27145-4:2012(E)
Road vehicles — Implementation of World-Wide Harmonized
On-Board Diagnostics (WWH-OBD) communication
requirements —
Part 4:
Connection between vehicle and test equipment
1 Scope
This part of ISO 27145 defines the requirements to successfully establish, maintain and terminate communication
with a vehicle that implements the requirements of the WWH-OBD GTR (Global technical regulation No. 5; see
Reference [16]). This requires plug and play communication capabilities for the vehicle as well as for any test
equipment that intends to establish communication with a vehicle. This part of ISO 27145 details all the OSI
layer requirements to achieve this goal.
This part of ISO 27145 is intended to become the single communication standard for access to information
relating to vehicle on-board diagnostics (VOBD). To allow for a smooth migration from the existing communication
standards to this future world-wide standardized communication standard, the communication concept as
specified in this part of ISO 27145 is based on two different data links:
— Diagnostic communication over Controller Area Network (DoCAN), ISO 15765-4;
— Diagnostic communication over Internet Protocol (DoIP), ISO 13400 (all parts).
NOTE It is intended that this part of ISO 27145 will be extended as necessary upon introduction of additional
communication media.
IMPORTANT — Use cases deriving from country-specific implementation of GTR No. 5 into local
legislation are not included in this part of ISO 27145.
2 Normative references
The following referenced documents are indispensable for the application 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 13400-2:2012, Road vehicles — Diagnostic communication over Internet Protocol (DoIP) — Part 2:
Transport protocol and network layer services
ISO 13400-3, Road vehicles — Diagnostic communication over Internet Protocol (DoIP) — Part 3: Wired
vehicle interface based on IEEE 802.3
ISO 14229-1, Road vehicles — Unified diagnostic services (UDS) — Part 1: Specification and requirements
ISO 14229-2, Road vehicles — Unified diagnostic services (UDS) — Part 2: Session layer services
ISO 15765-2, Road vehicles — Diagnostic communication over Controller Area Network (DoCAN) — Part 2:
Transport protocol and network layer services
ISO 15765-4:2011, Road vehicles — Diagnostic communication over Controller Area Network (DoCAN) —
Part 4: Requirements for emissions-related systems
ISO 27145-1, Road vehicles — Implementation of World-Wide Harmonized On-Board Diagnostics (WWH-OBD)
communication requirements — Part 1: General information and use case definition
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ISO 27145-4:2012(E)
ISO 27145-2, Road vehicles — Implementation of World-Wide Harmonized On-Board Diagnostics (WWH-OBD)
communication requirements — Part 2: Common data dictionary
ISO 27145-3, Road vehicles — Implementation of World-Wide Harmonized On-Board Diagnostics (WWH-OBD)
communication requirements — Part 3: Common message dictionary
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 27145-1, ISO 27145-2 and
ISO 14229-1 apply.
3.2 Abbreviated terms
CAN controller area network
DHCP dynamic host configuration protocol
DID data identifier
DoCAN diagnostic communication over CAN
DoIP diagnostic communication over internet protocol
DTC diagnostic trouble code
ECU electronic control unit
FMI failure mode indicator
FTB failure type byte
GTR global technical recommendation
IP internet protocol
N_PDU network layer protocol data unit
NRC negative response code
OBD on-board diagnostics
OSI open systems interconnection
SA source address
SPN suspect parameter number
T_PDU transport/network layer protocol data unit
TA target address
TCP transmission control protocol
WWH-OBD world-wide harmonized on-board diagnostics
VOBD vehicle on-board diagnostics
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ISO 27145-4:2012(E)
4 Conventions
The ISO 27145 series is based on the conventions discussed in the OSI Service Conventions (ISO/IEC 10731)
as they apply to diagnostic services.
5 Document overview
Figure 2 shows the reference documents for the ISO 27145 series.
The ISO 27145 series specifies or includes the following references:
a) ISO 27145-1 specifies the general structure of the ISO 27145 series and the WWH-OBD GTR
applicable use cases.
b) ISO 27145-2 specifies the common data dictionary with references to:
1) SAE J1930-DA, which defines the terms, definitions, abbreviated terms, etc.;
2) SAE J1939 Companion Spreadsheet, which specifies the SPNs;
3) SAE J1939-73:2010, Appendix A, which specifies the FMIs;
4) SAE J1979-DA, which specifies all data items;
5) SAE J2012-DA, which specifies the DTC definitions and FTB definitions.
NOTE The SAE J1939 series of documents is concerned with the definition of emissions-related SPNs and FMIs
for use as DTCs.
c) ISO 27145-3 specifies the diagnostic services defined in ISO 14229-1 that are applicable to WWH-OBD GTR.
d) ISO 14229-2 specifies the standardized service primitive interface to separate application and session
layers from protocol transport and network layers.
e) This part of ISO 27145 specifies the initialization procedure and includes references to:
1) ISO 15765-4 DoCAN;
2) ISO 13400 (all parts) DoIP.
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ISO 27145-4:2012(E)
Unified diagnostic services (UDS)
ISO 27145-1
WWH-OBD
general information and
use case definition
ISO 27145-3
SAE J1930-DA
ISO 14229-1 UDS
1 : 1
WWH-OBD
subset Terms , .
specification and
OSI layer 7
common message
requirements
Application
dictionary
SAE J1979-DA
1 : 1
PIDs, MIDs, RIDs,
ITIDs
ISO 27145-2
WWH-OBD
OSI layer 6
common data
Presentation
dictionary
SAE J2012-DA
1 : 1
WWH-OBD DTCs
SAE J1939 Companion
ISO 14229-2 UDS ISO 14229-2 UDS
1 : 1
OSI layer 5
Spreadsheet
session layer interfaces session layer interfaces
subset
Session SAE J1939-73:2011,
Appendix A
Standardized service primitive interface
Diagnostic communication over CAN and Internet Protocol
DoCAN
DoIP
OSI layer 4
Transport
ISO 15765-2 DoCAN
ISO 13400-2 DoIP
transport protocol
transport protocol
and
and
network
network
layer services
layer services
OSI layer 3
Network
ISO 27145-4
ISO 15765-4 DoCAN
WWH-OBD
requirements for
emissions-related connection between
systems vehicle and test
equipment
OSI layer 2
ISO 11898-1 CAN
Data link

data link layer
ISO 13400-3 DoIP
and physical signalling
wired vehicle
interface based
ISO 11898-2 CAN
on IEEE 802.3
high-speed
medium access unit
OSI layer 1
Physical
Figure 2 — Implementation of WWH-OBDonCAN and WWH-OBDonIP document reference
according to OSI model
6 Vehicle and external test equipment connection requirements
6.1 Overview
To provide a future-oriented long-term stable communication standard which is based on existing industry
communication standards while allowing for backward-compatibility to existing automotive networks, ISO 27145
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ISO 27145-4:2012(E)
is designed to support different types of connections between external test equipment and a vehicle. Regardless
of the underlying physical layer, data link and network layer the other parts of ISO 27145 remain unaltered.
a) CAN-based wired connection (see Clause 7)
This is the type of connection which describes the use of WWH-OBD communication services on an
existing ISO 15765-4-compliant vehicle interface. It has been defined to allow for a smooth migration from
a CAN-based vehicle interface to an Ethernet-based connection to a vehicle.
b) DoIP over Ethernet wired connection (see Clause 8)
This is the type of connection which utilizes the Internet Protocol as the network layer on a Fast Ethernet
(IEEE 802.3) connection.
6.2 Data link independent requirements
WWH-OBD-compliant servers/ECUs are required to support the InfoType “ECUNAME” with services
readDataByIdentifier 0x22 and dataIdentifier 0xF80A (see SAE J1979-DA). The mapping between a
server/ECU logical address and the name (ECUNAME) of the server/ECU shall be performed by the external
test equipment.
6.3 Support of only one WWH-OBD-compliant external test equipment at a time
The in-vehicle WWH-OBD system shall support only one type of WWH-OBD-compliant external test
equipment at a time:
— If the vehicle supports DoCAN, then the WWH-OBD-compliant external test equipment shall use the source
addresses (SA) specified in ISO 15765-4:2011, 10.5, which deals with mapping of diagnostic addresses.
— If the vehicle supports DoIP, then the WWH-OBD-compliant external test equipment shall use the SA
0xE000 specified in ISO 13400-2:2012, Table 39, which gives an overview of logical addressing.
7 Wired CAN connection based on ISO 15765-4
7.1 Network scenario requirements
Using ISO 11898-1 and ISO 11898-2 (CAN) and ISO 15765-4 (DoCAN), a variety of network scenarios can be used
to access vehicles for the use cases defined in ISO 27145-1. See ISO 14229-2 for network scenario examples.
7.2 Initialization sequence
The external test equipment shall support the initialization sequence as specified in ISO 15765-4.
7.3 ISO 27145-3 WWH-OBD protocol validation sequence
The external test equipment shall support the ISO 27145-3 WWH-OBD protocol validation sequence specified
in ISO 15765-4.
7.4 Application layer — DoCAN
7.4.1 General
All application-specific requirements for data content and formatting shall be supported as specified in
ISO 27145-2 and ISO 27145-3.
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ISO 27145-4:2012(E)
7.4.2 Diagnostic protocol communication types
The following communication types shall be supported for the diagnostic protocol implementation for WWH-OBD
on CAN as specified in ISO 14229-2:
a) functional communication;
b) physical communication.
The following WWH-OBD communication types on DoCAN shall be supported by WWH-OBD-compliant
servers/ECUs (for details, see ISO 14229-2):
— functional communication during defaultSession;
— functional communication during defaultSession with enhanced response timing;
— physical communication during defaultSession;
— physical communication during defaultSession with enhanced response timing.
Each diagnostic service specified in ISO 27145-3 shall be transmitted by the external test equipment with the
addressing method (functionally, physically) as specified in ISO 27145-3. Specific requirements on the use of
individual services with either functional or physical addressing are given in ISO 27145-3.
EXAMPLE Short diagnostic requests (less than 7 bytes) which are supported by most of the ECUs can be transmitted
using functional addressing, while requests for multiple data identifiers (DIDs) (see ISO 27145-2) which are explicitly
requested from a single server/ECU shall be requested using physical addressing.
7.4.3 Maximum number of WWH-OBD servers/ECUs
The maximum number of WWH-OBD-compliant servers/ECUs is limited by the address range definitions
in ISO 15765-4.
7.4.4 Diagnostic protocol timing parameters
The application layer timing parameter values for the default diagnostic session shall be in accordance
with ISO 27145-3.
For all diagnostic services specified in ISO 27145-3, the possibility of the server requesting an enhanced
response-timing window via a negative response message, including a negative response code (NRC) 0x78
(requestCorrectlyReceived-ResponsePending), shall be supported if specified for the diagnostic service in
ISO 14229-2 (see P4 ).
Server
7.4.5 External test equipment logical addresses
The external test equipment implementing the use cases defined in ISO 27145-1 shall implement the CAN
identifiers and the address as specified in ISO 15765-4 for the external legislated diagnostic test equipment
when requesting WWH-OBD data from a WWH-OBD-compliant vehicle.
7.4.6 Server/ECU logical addressing
A WWH-OBD-compliant vehicle shall implement the CAN identifiers and the address as specified in
ISO 15765-4 for each WWH-OBD-compliant server/ECU.
7.5 Presentation layer
All presentation-layer-specific requirements for data content and formatting shall be supported as defined
in ISO 27145-2.
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ISO 27145-4:2012(E)
7.6 Session layer
All WWH-OBD communication shall take place during the default diagnostic session; therefore, no session
layer timing handling is required for WWH-OBD communication. Further details are given in ISO 14229-2.
There shall always be exactly one diagnostic session active in a WWH-OBD-related server/ECU. A
WWH-OBD-related server/ECU shall always start the default diagnosti
...