ISO 11992-4:2014

DRAFT INTERNATIONAL STANDARD ISO/DIS 11992-4
ISO/TC 22/SC 3 Secretariat: DIN
Voting begins on Voting terminates on

2012-02-21 2012-07-21
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION  •  МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ  •  ORGANISATION INTERNATIONALE DE NORMALISATION

Road vehicles — Interchange of digital information on electrical
connections between towing and towed vehicles —
Part 4:
Diagnostic communication
Véhicules routiers — Échange d'informations numériques sur les connexions électriques entre véhicules
tracteurs et véhicules tractés —
Partie 4: Communication de diagnostic
[Revision of first edition (ISO 11992-4:2005)]
ICS 43.040.15
In accordance with the provisions of Council Resolution 15/1993 this document is circulated in
the English language only.
Conformément aux dispositions de la Résolution du Conseil 15/1993, ce document est
distribué en version anglaise seulement.

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©  International Organization for Standardization, 2012

ISO/DIS 11992-4
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ii © ISO 2012 – All rights reserved

ISO/DIS 11992-4
Contents Page
Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Symbols and abbreviated terms .6
5 General definitions .7
5.1 Conventions .7
5.2 Use case definitions .7
5.3 Diagnostic applications .9
5.4 Vehicle network architecture .9
5.5 Diagnostic communication channels . 11
6 Application layer requirements . 12
6.1 Application layer services . 12
6.2 Application layer protocol . 12
6.3 Timing definition . 12
6.4 Overview on diagnostic services . 14
6.5 Non-applicable or restricted services . 15
6.6 Basic diagnostic services . 15
6.7 Enhanced diagnostic services . 18
7 Presentation layer requirements . 18
8 Session layer requirements . 18
9 Network layer requirements . 18
9.1 General . 18
9.2 Message routing . 18
9.3 Establishing, maintaining and termination of connections . 18
9.4 Diagnostic communication channels (DCC) . 19
9.5 Network layer service parameter . 19
9.6 Network layer gateway function . 22
9.7 Network layer protocol timing . 22
10 Transport layer requirements . 23
10.1 General . 23
10.2 Transport layer service parameters . 23
11 Data link layer requirements . 24
12 Physical layer requirements . 24
Annex A (normative) Basic diagnostic service parameters . 25
Annex B (normative) Address definitions . 30
Annex C (informative) Message routing examples . 32
Bibliography . 37

2 © ISO 2012 – All rights reserved

ISO/DIS 11992-4
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 11992-4 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3,
Electrical and electronic equipment.
ISO 11992 consists of the following parts, under the general title Road vehicles — Interchange of digital
information on electrical connections between towing and towed vehicles:
 Part 1: Physical layer and data-link layer
 Part 2: Application layer for brakes and running gear equipment
 Part 3: Application layer for equipment other than brakes and running gear
 Part 4: Diagnostic communication
ISO/DIS 11992-4
Introduction
This part of the international standard has been established in order to define the implementation of a
diagnostic data interchange between a commercial vehicle and its towed vehicle(s), including communication
between towed vehicles, using a Controller Area Network (CAN) serial data link according to ISO 11992-1 and
based on the definitions for unified diagnostic services and their implementation on CAN given in the
ISO 14229 and ISO 15765 document series.
To achieve this, the document is based on the Open Systems Interconnection (OSI) Basic Reference Model in
accordance with ISO 7498 and ISO/IEC 10731, which structures communication systems into seven layers.
When mapped on this model, the services used by a diagnostic tester (client) and an Electronic Control Unit
(ECU, server) based on this document are broken into the following layers according to Table 1:
 Application layer (layer 7), based on ISO 14229-1 and ISO 14229-3
 Presentation layer (layer 6), vehicle manufacturer / system supplier specific or ISO 22901 ODX
 Session layer services (layer 5), based on ISO 14229-2
 Transport layer services (layer 4), based on ISO 15765-2
 Network layer services (layer 3), based on ISO 15765-2
 Data link layer (layer 2), specified in ISO 11898-1
 Physical layer (layer 1), specified in ISO 11992-1
This document does not include any redundant information of the documents listed in this introduction. It
focuses on
 additional requirements specific to the implementation of UDS on a ISO 11992 network, and
 specific restrictions in the implementation of UDS on a ISO 11992 network.
In case of any contradictions the definitions given in this document shall have precedence.
Table 1 — International standards applicable to the O.S.I. layers
Applicability OSI 7 layer Diagnostics services on communication
between commercial vehicles and their towed vehicles
Application (layer 7) ISO 11992-4, ISO 14229-1, ISO 14229-3
Presentation (layer 6) vehicle manufacturer specific
Seven layer
Session (layer 5) ISO 11992-4, ISO 14229-2
according to
ISO/IEC 7498 Transport (layer 4) ISO 11992-4, ISO 15765-2
and ISO/IEC
Network (layer 3) ISO 11992-4, ISO 15765-2
Data link (layer 2) ISO 11898-1
Physical (layer 1) ISO 11992-1

4 © ISO 2012 – All rights reserved

DRAFT INTERNATIONAL STANDARD ISO/DIS 11992-4
Road vehicles — Interchange of digital information on electrical
connections between towing and towed vehicles —
Part 4:
Diagnostic communication
1 Scope
This document specifies the diagnostic communication over CAN on a serial data link between the towing and
towed vehicle(s) of a commercial vehicle and its trailer(s) according to ISO 11992-2 or ISO 11992-3, which
allow a diagnostic tester (client) to control diagnostic functions in an on-vehicle Electronic Control Unit (server)
embedded in a road vehicle using the communication gateways between the vehicles.
It defines the data link layer specific implementation of the unified diagnostic communication requirements
mainly given in the ISO 14229 and ISO 15765 document series by additional requirements and restrictions
specific to the implementation of UDS on an ISO 11992 network.
This document does not apply to any non-diagnostic message transmission use of the communication data
link between two Electronic Control Units.
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 11992-2, Road vehicles — Interchange of digital information on electrical connections between towing
and towed vehicles — Part 2: Application layer for brakes and running gear
ISO 11992-3, Road vehicles — Interchange of digital information on electrical connections between towing
and towed vehicles — Part 3: Application layer for equipment other than brakes and running gear
ISO 14229-1:2011, Road vehicles — Unified diagnostic services (UDS) — Part 1: Specification and
requirements
ISO 14229-2:2011, Road vehicles — Unified diagnostic services (UDS) — Part 2: Session layer services
ISO 14229-3:2011, Road vehicles — Unified diagnostic services (UDS) — Part 3: Unified diagnostic services
on CAN implementation (UDSonCAN)
ISO 15031-6 Road vehicles — Communication between vehicle and external equipment for emissions-related
diagnostics — Part 6: Diagnostic trouble code definitions
ISO 15765-1:2010, Road vehicles — Diagnostic communication over Controller Area Networks (DoCAN) —
Part 1: General information and use case definition
ISO 15765-2:2010, Road vehicles — Diagnostic communication over Controller Area Networks (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 11992-1, ISO 11992-2,
ISO 11992-3, ISO 14229-1, ISO4229-2, ISO 14229-3, ISO-15765-1 and ISO 15765-2 and the following apply.
ISO/DIS 11992-4
3.1
Diagnostic network
The diagnostic network, as a whole, contains all clients and servers that can communicate with each other on
the different vehicles of a road-train, as well as the diagnostic gateways between the vehicles.
3.2
Diagnostic sub-network
All clients and servers of a sub-network are connected to the same vehicle's diagnostic network. Sub-
networks are separated by the gateways between the vehicles.
3.2
Diagnostic gateway
A diagnostic gateway is a node in the network that is physically connected to two (or more) sub-networks and
has the ability to transfer diagnostic messages between the sub-networks.
4 Symbols and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 11898-1, ISO 11992-1,
ISO 14229-1, ISO 14229-3 and ISO 15765-2 and the following apply.
A_PDU Application layer protocol data unit
BS block size
CAN Controller area network
CAN-ID CAN identifier
Cvt convention
DCC Diagnostic communication channel
DID Data identifier
DLC Data length code
DP Data page
DTC Diagnostic trouble code
ECU Electronic control unit
EDP Extended data page
FS Flow status
N_AE Network layer address extension
N_AI Network layer address information
N_SA Network layer source address
N_TA Network layer target address
N_TAtype Network layer target address type
N_WFTmax Network layer maximum number of wait frames
P Priority
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ISO/DIS 11992-4
PDU Protocol data unit
PF Parameter format
PGN Parameter group number
PS Parameter specific
RA Remote address
SA Source address
SID Service identifier
STmin Separation time
TA Target address
TA_type Target address type
5 General definitions
5.1 Conventions
This document is based on the conventions used in ISO 14229-1 and the underlying OSI Service Conventions
(ISO/IEC 10731:1994) as they apply for diagnostic services.
These conventions specify the interactions between the service user and the service provider. Information is
passed between the service user and the service provider by service primitives, which may convey
parameters.
5.2 Use case definitions
5.2.1 General
This section lists the individual use cases which will be covered by the diagnostic communication over
ISO 11992 protocol at the following areas:
 Vehicle / ECU engineering (development)
 Vehicle / ECU manufacturing (production plant, assembly line)
 Service (dealership, aftermarket repair shop)
 Retrieval of information between connected vehicles
The following use cases are supported by the communication protocol
5.2.2 Use case 1 – Driver information
Driver information specifies the use case to enable an in-vehicle information retrieval system at the
commercial vehicle to qualify readiness of the towed vehicle(s).
In this case usually an information retrieval entity is installed in the commercial vehicle that gets data from the
various ECUs located in the road train, including the towed vehicle(s), and forwards relevant information about
the road worthiness of the road train to the driver.
ISO/DIS 11992-4
5.2.3 Use case 2 – Vehicle inspection and repair
Vehicle inspection and repair specifies the use case to enable an external test equipment connected to the
road-train to qualify readiness of any vehicle and to perform vehicle diagnostic fault tracing as part of a repair.
In this case usually an external test equipment is connected to the commercial vehicle and request road train
data which can be qualified to determine the readiness of the vehicle(s) or to perform vehicle diagnostic fault
tracing as part of a repair.
5.2.4 Use case 3 – ECU/vehicle software reprogramming
ECU/vehicle software reprogramming specifies the use case to reprogram the ECU(s) of a towed vehicle
through its data communication channel.
In this case usually an external programming equipment is connected to the commercial vehicle or directly to
a towed vehicle and uses diagnostic communication to (re-)program or configure ECU(s) located in the towed
vehicle.
5.2.5 Use case 4 – ECU/vehicle assembly line inspection and repair
ECU/vehicle assembly line inspection and repair specifies the use case to enable an external test system
connected to a towed vehicle to support the assembly line inspection and repair of towed vehicle ECU
systems.
In this case usually an external test equipment is connected to the commercial vehicle or directly to the towed
vehicle and uses diagnostic services to determine the readiness of the vehicle(s) or to perform vehicle
diagnostic fault tracing as part of a repair.
5.2.6 Use case 5 – Multi-purpose data transfer between vehicles
Multi-purpose data transfer between vehicles specifies the use case to enable ECU(s) in any vehicle of the
road-train to retrieve information from other vehicle's ECU(s).
In this case an ECU may use diagnostic services to retrieve information from another ECU for various
purposes.
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ISO/DIS 11992-4
5.3 Diagnostic applications
The diagnostic applications are divided into two types
 Basic diagnostics
The purpose of the basic diagnostics is to provide vehicle independent identification and diagnostic
information. All basic diagnostic functions and services shall be provided under all operation conditions in
the default diagnostic session without the need for specific access rights.
 Enhanced diagnostics
The support and the conditions under which enhanced diagnostic functions and services are provided are
manufacturer/system supplier specific. It is in the responsibility of the manufacturer/system supplier to
secure a server against unauthorized access and to ensure performance and safe operation in all
operation modes allowing enhanced diagnostics.
Functions, services and protocols of the OSI layers 1 to 4 shall be identical for basic diagnostics and
enhanced diagnostics. For OSI layers 5 to 7 the implementation of functions, services and protocols are
varying according the definitions given in this document.
5.4 Vehicle network architecture
This document supports the diagnostic communication between a commercial vehicle and its towed vehicles
as illustrated in Figure 1.
1 2 3 4
Key:
1 truck / commercial vehicle (position #0)
2 trailer / towed vehicle position #1
3 dolly / towed vehicle position #2
4 trailer / towed vehicle position #3
Figure 1 — Example of a possible road train configuration
ISO/DIS 11992-4
Subnet definitions shall be as follows
 The commercial vehicle's logical network shall expand over
 all servers and clients located at the commercial vehicle, and
 the towed vehicle gateways
 The physical network segments between each towing and towed vehicle shall be part of the local logical
network of the commercial vehicle and share the logical addressing scheme of the commercial vehicle.
 Each towed vehicle shall implement its own local logical network(s) with its own addressing scheme.
 Server and client entities that are not located at the same logical network shall be addressed and
identified by means of remote network addressing.
Details about the used addressing scheme are given in clause 9 (Network layer ).
Figure 2 shows an example of the vehicle network architecture.
Commercial
Client 1 vehicle logical
network
Commercial Towed Towed
vehicle vehicle #1 vehicle #2
gateway gateway gateway
Server 1 Server 1
Towed Towed
Server 2 Server 1 Server 2
Commercial
vehicle vehicle
vehicle local
local local
network
network network
Server 3 Server 2
Server 4 Server 3
Commercial vehicle Towed vehicle #1 Towed vehicle #2

Figure 2 — Vehicle network architecture example
10 © ISO 2012 – All rights reserved

ISO/DIS 11992-4
5.5 Diagnostic communication channels
This document specifies diagnostic requests sent from any of the vehicles to any other vehicle of a road-train.
For communication between vehicles defined diagnostic communication channels (DCC) shall be used as
defined in clause 9 based on the service data unit and application layer address mapping specification given
in ISO 14229-1.
An example is given in Figure 3 and Table 2
ISO 11992
DCC
241 (241) 1
test remote
gateway gateway
equipment server
(200) 200 62
Figure 3 — application layer address mapping example

Table 2 — application layer address mapping example
Message SA TA RA
The test equipment sends a remote diagnostic request message 241 200 62
The client gate receives the message and sends it out on the ISO 11992 bus 241 200 62
The server gate receives the message and sends it out on the server's vehicle local bus 1 62 241
The remote server receives the message and sends back a diagnostic response 62 1 241
The server gate receives the message and sends it out on the ISO 11992 bus 200 241 62
The client gate receives the message and sends it out on the client's vehicle local bus 200 241 62

The address mapping between the vehicle networks shall be done by the gateway entities and is specified in
this document. Address mapping at the vehicle's local networks is left open to the system builder. More
detailed examples are given in the (informative) Annex C.
ISO/DIS 11992-4
6 Application layer requirements
6.1 Application layer services
The application layer services as defined in ISO 14229-1 for client-server based systems shall be used to
perform functions such as test, inspection, monitoring, diagnosis or programming of on-board vehicle servers.
6.2 Application layer protocol
The application layer protocol as defined in ISO 14229-1 shall be used with the parameters defined in Table 3
at peer entity networks.
Table 3 — application layer parameters
Parameter Peer Definition Data range
network
SA_request client Local address of the client Any allowed client address except e.g. the specified
addresses given in Table B.1 — Towing / towed
vehicle data link — Physical addresses
server Local gateway address at Any gateway address according to the definitions
the vehicle the server is given in Table B.3 — Trailer local network —
located on Physical addresses
SA_response client Gateway address at the Any gateway address according to the definitions
given in Table B.1 — Towing / towed vehicle data
vehicle the server is
located on link — Physical addresses
server Local address of the Any allowed server address within the server's
server vehicle network.
TA_request client Gateway address at the Any gateway address according to the definitions
given in Table B.1 — Towing / towed vehicle data
vehicle the server is
located on link — Physical addresses or Table B.2 — Towing /
towed vehicle data link — Functional addresses
server Local address of the Any allowed server address within the server's
server vehicle network.
TA_response client Local address of the client Any allowed client address except e.g. the specified
addresses given in Table B.1 — Towing / towed
vehicle data link — Physical addresses
server Local gateway address at Any gateway address according to the definitions
the vehicle the server is given in Table B.3 — Trailer local network —
located on Physical addresses
RA client Local address of the Any allowed server address within the server's
server vehicle network.
server Local address of the client Any address except the specified addresses given
in Table B.1 — Towing / towed vehicle data link —
Physical addresses
TAtype Target address type to be {   |
used for TA  }

6.3 Timing definition
6.3.1 General
This sub-clause specifies the message timing parameters and how they apply to a client and a server.
12 © ISO 2012 – All rights reserved

ISO/DIS 11992-4
6.3.2 Message timing parameter values
The message timing parameter values for the default diagnostic session shall be in accordance with
ISO 14229-3 and the deviations specified in Table 4.
Table 4 — Message timing parameters
Timing Definition Minimum Maximum
parameter
ΔP2 The ΔP2 parameter is defined to be the worst case system network 0 ms 200 ms
design-dependent message transmission delays such as delays
introduced by gateways between towing and towed vehicles and bus-
load arbitration delay.
P2
The P2 parameter is a performance requirement for the 0 ms 50 ms
server Server
server/ECU to start with the response message after the reception of
a request message.
P2 P2 + ΔP2 250 ms —
client
server, max max
P2* The P2* parameter is a performance requirement for the server to 0 ms 5 000 ms
server server
start with the response message after the transmission of a negative
response message with the negative response code 78 (enhanced
response timing)
P2* P2* + ΔP2 5 200 ms —
client
server, max max
6.3.3 Unsolicited response messages
Unsolicited response messages are not applicable for this document.
ISO/DIS 11992-4
6.4 Overview on diagnostic services
The purpose of Table 5 is to reference all unified diagnostic services as they are applicable for an
implementation of UDS on ISO 11992. The table contains the sum of all applicable services. Certain
applications using this document may restrict the number of useable services and may categorize them in
certain application areas/diagnostic sessions (default session, extended session, etc.).
Table 5 — Overview of applicable ISO 14229-1 Unified diagnostic services
Diagnostic service name SID Specification Document
(ISO 14229-1) value reference
Diagnostic and Communication Management Functional Unit
DiagnosticSessionControl 10 No specific requirements —
ECUReset 11 No specific requirements —
SecurityAccess 27 No specific requirements —
CommunicationControl 28 Restricted use 6.5
TesterPresent 3E No specific requirements —
AccessTimingParameters 83 Not supported 6.5
SecuredDataTransmission 84 No specific requirements —
ControlDTCSetting 85 No specific requirements —
ResponseOnEvent 86 Not supported 6.5
LinkControl 87 Not supported 6.5
Data Transmission Functional Unit
ReadDataByIdentifer 22 Data link layer specific definitions exist 6.6.3
ReadMemoryByAddress 23 No specific requirements —
ReadScalingDataByIdentifier 24 No specific requirements —
ReadDataByPeriodicIdentifier 2A Not supported 6.5
DynamicallyDefineDataIdentifier 2C No specific requirements —
WriteData ByIdentifier 2E No specific requirements —
WriteMemoryByAddress 3D No specific requirements —
Stored Data Transmission Functional Unit
ReadDTCInformation 19 Data link layer specific definitions exist 6.6.2
ClearDiagnosticInformation 14 Data link layer specific definitions exist 6.6.2
Input/Output Control Functional Unit
InputOutputControlByIdentifier 2F No specific requirements —
Remote Activation Of Routine Functional Unit
RoutineControl 31 No specific requirements —
Upload/Download Functional Unit
RequestDownload 34 No specific requirements —
RequestUpload 35 No specific requirements —
TransferData 36 No specific requirements —
RequestTransferExit 37 No specific requirements —
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ISO/DIS 11992-4
6.5 Non-applicable or restricted services
The following services are not applicable for implementation on ISO 11992 and are not within the scope of this
document or may be used under restrictions.
 CommunicationControl
Disabling the normal communication specified in ISO 11992-2 between towing and towed vehicles is not
permitted by UNECE Regulation 13 [5].
 AccessTimingParameter
This service is not applicable as there is no use case on a CAN based system.
 ResponseOnEvent
This service is not supported as there is no specification given for the communication between the
gateways for that type of communication.
 LinkControl
This service shall not be supported during communication between towing and towed vehicles as it is not
supported by a data link based on ISO 11992-1.
 ReadDataByPeriodicIdentifier
This service is not supported as there is no specification given for the communication between the
gateways for that type of communication.
6.6 Basic diagnostic services
6.6.1 Services
Within the scope of basic diagnostic services the following diagnostic services shall be supported
 ReadDTCInformation, as specified in sub-clause 6.6.2
 ReadDataByIdentifier, as defined in sub-clause 6.6.3
The diagnostic services specification includes tables which list diagnostic services and respective service
primitive parameters. For all services and service primitive parameters the presence is specified by the
convention values (Cvt) in Table 6.
Table 6 — diagnostic service primitive parameter conventions
Cvt Name Description
M Mandatory The service or service primitive parameter has to be present.
C Conditional The service or service primitive parameter can be present, based on certain criteria (e.g.
due to a certain sub-function).
S Selection The service or service primitive parameter is mandatory (unless otherwise specified) and
is a selection from a given list of services or service primitive parameters.
U User option The service or service primitive parameter may or may not be present, depending on
dynamic usage by the user.
NOTE A service identifier marked as mandatory does not imply that this service has to be supported.

ISO/DIS 11992-4
6.6.2 ReadDTCInformation service
6.6.2.1 General description
This service allows a client to read the status of server resident Diagnostic Trouble Code (DTC) information
from any server or group of servers within a vehicle as defined in ISO 14229-1. Within the scope of basic
diagnostics this service shall allow the client to do the following:
 Retrieve the number of DTC's matching a client defined severity mask,
 Retrieve the list of DTC's matching a client defined severity mask record,
 Retrieve severity information for a client defined DTC
Other sub-functions may be supported within the scope of enhanced diagnostics.
6.6.2.2 Request message sub-function definition
The server shall support the request and response service messages as defined in ISO 14229-1 for the sub-
functions listed in Table 7
Table 7 — ReadDTCInformation sub-functions for basic diagnostics
Value Definition Cvt
07 reportNumberOfDTCBySeverityMaskRecord M
This parameter specifies that the server shall transmit to the client the number of DTC's
matching a client defined severity mask record.
08 reportDTCBySeverityMaskRecord M
This parameter specifies that the server shall transmit to the client a list of DTC's and
corresponding statuses matching a client defined severity mask record.
09 reportSeverityInformationOfDTC U
This parameter specifies that the server shall transmit to the client the severity information
of a specific DTC specified in the client request message.

6.6.2.3 Request and response message data parameter definition
The server shall support the message data parameter definition as given in ISO 14229-1 with the deviations
given in Table 8.
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ISO/DIS 11992-4
Table 8 — message data parameter definition
Definition
DTCAndSeverityRecord
This parameter record contains one or more groupings of DTCSeverity, DTCFunctionalUnit, DTCHighByte,
DTCMiddleByte, DTCLowByte, and statusOfDTC of ISO11992-4DTCFormat with the details given in
annex A.3
DTCFormatIdentifier
This 1-byte parameter value defines the format of a DTC reported by the server and shall have this values
0 to 2 reserved, not used
3  ISO_11992-4_DTCFormat
4 to 255 reserved, not used
DTCMaskRecord [DTCHighByte, DTCMiddleByte, DTCLowByte]
The decoding of the DTCHighByte, DTCMiddleByte and DTCLowByte shall be according to the ISO 11992-4
specification. This format is identified by the DTCFormatIdentifier = ISO_11992-4_DTCFormat.
Definitions are given in annex A.3
DTCSeverityMaskRecord [DTCSeverityMask, DTCStatusMask]
DTCSeverityMaskRecord is a 2-byte value containing the DTCSeverityMask and the DTCStatusMask as
given in annex A.3
FunctionalGroupID
The FunctionalGroupID parameter shall be supported as given in annex A.3

6.6.3 ReadDataByIdentifier service
6.6.3.1 General
This service shall be used to request information from a server identified by a dataIdentifier. Within the scope
of basic diagnostics only one dataIdentifier shall be present in a request message.
6.6.3.2 Request message data parameter definition
The service parameter of the ReadDataByIdentifier service request shall be supported for basic diagnostics as
specified in Table 9 with the dataIdentifier specified in annex A.2.1.
Table 9 — ReadDataByIdentifier request parameters
A_Data byte Parameter name Cvt Value
#1 ReadDataByIdentifier request service identifier M 22
dataIdentifier[] = {
#2 Byte 1 (MSB) M 00 -FF
16 16
#3 Byte 2 (LSB) } M 00 -FF
16 16
6.6.3.3 Response message data parameter definition
The service parameter of the ReadDataByIdentifier service response shall be supported for basic diagnostics
as specified in Table 10 with the dataIdentifier and dataRecord as specified in annex A.2.1.
ISO/DIS 11992-4
Table 10 — ReadDataByIdentifier positive response parameters
A_Data byte Parameter name Cvt Value
#1 ReadDataByIdentifier response service identifier M 62
dataIdentifier[] = {
#2 byte 1 (MSB) M 00 -FF
16 16
#3 byte 2 (LSB) } M 00 -FF
16 16
dataRecord[] = {
#4 data#1 M 00 -FF
16 16
: : : :
#(m-1)+4 data#m } U 00 -FF
16 16
6.7 Enhanced diagnostic services
Within the scope of enhance diagnostics all services defined to be applicable in sub-clause 6.4 with the
exclusions given in sub-clause 6.5 may be used as specified in ISO 14229-3.
7 Presentation layer requirements
No specific presentation layer functions have been specified.
8 Session layer requirements
No specific session layer functions have been specified.
9 Network layer requirements
9.1 General
This section specifies the network layer requirements on the ISO 11992 data link. Network layer specification
is given in ISO 15765-2 with the following amendments. In case of differences the specifications of this part of
ISO 11992 shall have precedence.
9.2 Message routing
The network layer entities shall provide message routing functions to support communication between servers
and clients on the commercial vehicle local network and the towed vehicle(s) local network(s). Examples are
given in the (informative) Annex C.
9.3 Establishing, maintaining and termination of connections
For the diagnostic data transmission between towing and towed vehicles the following limitations apply:
a) Multiframe (segmented) messages shall use point to point (1 to 1) connections with physical addressing
only.
b) Single frame messages may use multi point (1 to n) connectionless transmission with functional
addressing or point to point (1 to 1) connections with physical addressing.
In case of a multiframe message, initiated by the commercial vehicle, connections between peer entities shall
be established and maintained automatically with the transmission/reception of the first flow control frame
from the receiver of the message. A connection shall be automatically terminated after the
18 © ISO 2012 – All rights reserved

ISO/DIS 11992-4
transmission/reception of the last consecutive frame or the expiration of a correspondent network layer
timeout. Only one connection between two peer network layer entities shall be allowed at the same time.
In case of communication, initiated by a towed vehicle, connections between peer entities shall be established
and terminated by using the network service primitive DiagnosticCommunicationChannelControl (DCCC).
Only one connection between peer entities shall be allowed at the same time.
9.4 Diagnostic communication channels (DCC)
Each diagnostic communication channel (DCC) message is identified by its parameters as given in
ISO 11992-2 and ISO 11992-3 by
 its PGN DCC11, DCC12, DCC21 or DCC22
 the network target address N_TA and
 the network source address N_SA
9.5 Network layer service parameter
9.5.1 General
This sub-clause specifies the network layer service parameters used for diagnostic communication. All
parameters shall be used in accordance to the message definition given in ISO 11992-2, ISO 11992-3 and
ISO 15765-2 and the restrictions given in the following sub-clauses.
General requirements are
 The data link layer PDUs shall be used as defined in ISO 11992-2 and ISO 11992-3 using 29bit CAN-
identifiers.
 The CAN frame shall always be padded for transmission with 8 data bytes, i.e. DLC=8 according to
ISO 15765-2.
 Mapping of N_PDU fields shall be done according to ISO 15765-2 mixed addressing scheme using 29bit
CAN-identifiers.
For diagnostic service requests and responses the mapping parameters according to the definitions given in
this section shall apply. Vehicle network addresses in case of trailer vehicle shall be assigned according to the
definitions given in Table B.3 — Trailer local network — Physical addresses and Table B.4 — Trailer local
network — Functional addresses. Local addresses used at the commercial vehicle networks are usually
defined by the vehicle manufacturer.
9.5.2 Network layer target address (N_TA)
The network layer target address N_TA shall represent the target address of the network layer message
receiver on the ISO 11992 network and shall correspond to
 the destination address DA of the ISO 11992-2 and ISO 11992-3 address definition as given in
Table B.1 — Towing / towed vehicle data link — Physical addresses for network layer messages directed
from client to server entities
 the local network address the client is mapped to for network layer messages directed from server to
client entities.
9.5.3 Network layer source address (N_SA)
The network layer source address N_SA shall represent the source address of the network layer message
sender on the ISO 11992 network and shall correspond to
ISO/DIS 11992-4
 the source address SA of the ISO 11992-2 and ISO 11992-3 address definition as given in Table B.1 —
Towing / towed vehicle data link — Physical addresses for network layer messages directed from server
to client entities.
 the local network address the server is mapped to for network layer messages directed from client to
server entities.
9.5.4 Network layer address extension (N_AE)
The network layer address extension N_AE shall represent a server's address on the vehicle local network.
9.5.5 Target address type (N_TAtype)
The target address type to be used for TA shall be or < functional target address>.
9.5.6 Message addressing and mapping to CAN PDU
Remote network addressing is used by means of the mixed address format. The network layer address
information N_AI shall be encapsulated in the CAN_ID and the first byte of the CAN PDU. The relation
between network layer address information, PDU1 parameters and the CAN identifier usage according to
ISO 11992-2 and ISO 11992-3 shall be implemented as given Figure 4.
N_AI (network layer address information)
N_TAtype N_TA N_SA N_AE
MSB 29-bit CAN-ID bit position LSB CAN data field byte position
28 26 25 24 23 16 15 8 7 0 1 2 to 8
ISO 11992
P EDP DP PF PS SA Data field
CAN PDU
number of
3 1 1 8 8 8 8 56
bits
Figure 4 — Network layer address encoding
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ISO/DIS 11992-4
9.5.7 Message length
The parameter length identifies the number of message data bytes. The maximum length allowed is 255
...