ISO 16844-6:2004

INTERNATIONAL ISO
STANDARD 16844-6
First edition
2004-08-15

Road vehicles — Tachograph systems —
Part 6:
Diagnostics
Véhicules routiers — Systèmes tachygraphes —
Partie 6: Diagnostic




Reference number
ISO 16844-6:2004(E)
©
ISO 2004

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ISO 16844-6:2004(E)
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ISO 16844-6:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Abbreviated terms. 1
4 Overview and conventions. 2
5 Application layer services. 3
6 Application layer protocol. 3
7 Network layer (CAN only). 3
8 Data link layer. 4
9 Physical layer. 4
10 Addresses. 5
11 Parameters. 5
12 Diagnostic services. 5
Bibliography . 16

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ISO 16844-6:2004(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 16844-6 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3,
Electrical and electronic equipment.
ISO 16844 consists of the following parts, under the general title Road vehicles — Tachograph systems:
 Part 1: Electrical connectors
 Part 2: Recording unit, electrical interface
 Part 3: Motion sensor interface
 Part 4: CAN interface
 Part 5: Secured CAN interface
 Part 6: Diagnostics
 Part 7: Parameters
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ISO 16844-6:2004(E)
Introduction
ISO 16844 supports and facilitates the communication between electronic units and a tachograph; the
[1] [2]
tachograph being based upon Council Regulations (EEC) No. 3820/85 and (EEC) No. 3821/85 and their
[3] [4]
amendments Council Regulation (EEC) No. 2135/98 and Commission Regulation (EC) No. 1360/2002 .
Its purpose is to ensure the compatibility of tachographs from various tachograph manufacturers.
The basis of the digital tachograph concept is a recording unit (RU) that stores data related to the activities of
the drivers of a vehicle on which it is installed. When the RU is in normal operational status, the data stored in
its memory are made accessible to various entities such as drivers, authorities, workshops and transport
companies in a variety of ways: they may be displayed on a screen, printed by a printing device or
downloaded to an external device. Access to stored data is controlled by a smart card inserted in the
tachograph.
In order to prevent manipulation of the tachograph system, the speed signal sender (motion sensor) is
provided with an encrypted data link.
A typical tachograph system is shown in Figure 1.

Key
1 positive supply 3 speed signal, real time
2 battery minus 4 data signal in/out
Figure 1 — Typical tachograph system
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INTERNATIONAL STANDARD ISO 16844-6:2004(E)

Road vehicles — Tachograph systems —
Part 6:
Diagnostics
1 Scope
This part of ISO 16844 specifies diagnostic communication and services in tachograph systems used in road
vehicles, for both the controller area network (CAN) and K-line communication modes. It is also applicable for
programming purposes.
NOTE The diagnostic services base according to ISO 14229-1 and most services are common to the two
communication modes, CAN and K-line. With CAN, however, there is no need for a service to start the communication, as
the electronic control unit (ECU) always starts in the standard diagnostic session.
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 11898-1, Road vehicles — Controller area network (CAN) — Part 1: Data link layer and physical
signalling
ISO 14229-1, Road vehicles — Unified diagnostic services (UDS) — Part 1: Specification and requirements
ISO 14230-1, Road vehicles — Diagnostic systems — Keyword Protocol 2000 — Part 1: Physical layer
ISO 14230-2, Road vehicles — Diagnostic systems — Keyword Protocol 2000 — Part 2: Data link layer
ISO 15765-2, Road vehicles — Diagnostics on Controller Area Networks (CAN) — Part 2: Network layer
services
ISO 15765-3, Road vehicles — Diagnostics on Controller Area Networks (CAN) — Part 3: Implementation of
unified diagnostic services (UDS on CAN)
ISO 16844-7, Road vehicles — Tachograph systems — Part 7: Parameters
3 Abbreviated terms
Cvt. convention
M mandatory
U user option
C conditional
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ISO 16844-6:2004(E)
4 Overview and conventions
4.1 Overview
Figure 2 shows the tachograph diagnostic communication links and their layers, based on the OSI (open
systems interconnection) model.
NOTE The download protocol specification is not covered by this part of ISO 16844.

Figure 2 — Tachograph diagnostic communication links
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ISO 16844-6:2004(E)
4.2 Service description conventions
The service description conventions according to ISO 14229-1 shall be used.
5 Application layer services
The application layer services shall be implemented according to ISO 14229-1.
6 Application layer protocol
6.1 General
The application layer protocol shall be implemented according to ISO 15765-3 or ISO 14230-2, or both, as
well as according to the additional requirements of this clause.
6.2 Application layer timing
6.2.1 Timing parameters for CAN
For CAN, using the data link layer in accordance with ISO 11898-1, the ECU(s) shall respond to a request
message within P2 . The application timing parameter values for CAN and their requirements shall be in
CAN
accordance with Table 1.
Table 1 — Application layer timing parameters for CAN
Value
ms
Parameter Description/Requirement
min. max.
P2
0 100 Time between request message and the receipt of all unsegmented response messages and
CAN
all first frames of segmented response message(s).
Each ECU shall start sending its response message within P2 after the request message
CAN
has been correctly received.
P2* 0 5 000 Time between the successful reception of a negative response message with response code
CAN
78 and the next response message (positive or negative message).
hex

6.2.2 Timing parameters for K-line
The normal timing parameter, set in accordance with ISO 14230-2 (K-line), shall apply, using the data link
layer according to 8.2.
7 Network layer (CAN only)
7.1 General
This clause is applicable only when the data link layer in accordance with ISO 11898-1 (CAN) is used.
The network layer shall be implemented in accordance with ISO 15765-2, and according to the additional
requirements of 7.2.
NOTE The testerPresent service must be executed in parallel with another ongoing service.
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ISO 16844-6:2004(E)
7.2 Communication parameters
The parameter N_WFTmax shall be set to 0, meaning "No FlowControl wait frames are allowed".
The time parameter N_Br shall be < 100 ms.
The time parameter N_Cs shall be < 100 ms.
8 Data link layer
8.1 CAN data link layer
8.1.1 General
The CAN data link layer shall be used with the physical layer according to 9.1.
The data link is shared by the application layer specified in ISO 16844-4 and the diagnostic communication
specified in this part of ISO 16844.
8.1.2 Protocol
The protocol used shall be in accordance with ISO 16844-4.
8.1.3 Address coding method
The address coding method “Normal fixed addressing”, in accordance with ISO 15765-2, shall be used.
8.2 K-line data link layer
8.2.1 General
The K-line data link layer shall be used with the physical layer according to 9.2.
The requirements given in ISO 14230-2 shall apply, together with the restrictions given in 8.2.2 and 8.2.3 of
this part of ISO 16844.
8.2.2 Key bytes
Only the key word 2026 shall be used.
8.2.3 Initialisation
Only the fast initialisation shall be used.
8.2.4 Timing
The normal timing parameter set according to ISO 14230-2 shall apply.
9 Physical layer
9.1 CAN physical layer
The physical layer used for diagnostic communication on CAN shall be accordance with ISO 16844-4.
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ISO 16844-6:2004(E)
9.2 K-line physical layer
9.2.1 General
Additional to the CAN physical layer, the K-line physical layer in accordance with ISO 14230-1 may also be
used.
9.2.2 Configuration
Only K-line shall be used.
10 Addresses
10.1 General
All ECUs shall be able to respond to both functional and physical diagnostic addresses.
10.2 Functional addresses
The recording equipment shall respond to the functional address 238 as the system address and the
functional address 255 addressing all ECUs in the vehicle.
10.3 Physical addresses
Each ECU that is part of the recording unit shall have a physical address. The specific ECU containing the
data memory for recorded data shall have the address 238. All other addresses shall be vehicle-manufacturer-
specific.
11 Parameters
If a parameter value or a record value consists of more than one byte, the most significant byte shall always
be transmitted first, followed by bytes of decreasing significance.
12 Diagnostic services
12.1 General and overview
The diagnostic services shall be in accordance with ISO 14229-1 and with Table 2, which gives a summary
and an overview of all diagnostic services that may be available in the tachograph — specifying which
sessions and services are mandatory in the tachograph and in which diagnostic sessions the diagnostic
services are to be used.
Additional tachograph requirements, subfunctions, parameters and conventions of the diagnostic services are
given in 12.2 to 12.7.
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ISO 16844-6:2004(E)
Table 2 — Diagnostic service usage and identifier value summary and overview
Diagnostic services Diagnostic
...