Installation Manual

Electrical & Electronic Application And Installation Manual
Production Release Version 1.0
Page 247 12/16/2014
20.0 J1939 Parameters – Detailed Descriptions
Note: The PGN numbers are written in some documents in decimal form
(e.g.61444). This document will use the Hexadecimal form (e.g. F004) as it is
easier to remember and simpler to decode when using tools to analyse traffic
on the CAN J1939 bus.
20.1 Sending Messages to the Engine ECM
The engine ECU supports a large number of different J1939 PGN’s and
SPN’s including messages such as TSC1, OHECS, DM1 etc. Some of these
messages are requests from external devices such as TSC1 and others are
generated on transmitted by the ECM itself. Messages intended to be sent to
the engine ECM require that the correct source and destination addresses are
used.
20.1.1 Source Addressing
The source address is used to identify different components and electronic
control modules on a CAN bus, source address assignment is given in
appendix B of SAE J1939. Engine #1 source address is 00, and the service
tool source address is F0. Preferred J1939 source addresses vary between
industry groups, when designing a system, check tables B1-B7 in the SAE
J1939 standard to ensure the correct source address is allocated. The ECM
will accept messages from modules with any source address as long as it is
different to the source address of the engine ECM.
20.1.2 Destination Addressing
For messages controlling the engine functionality, such a TSC1 and OHECS,
the engine will only respond to these messages when sent with a destination
address of 00 (unless the ECM address has been changed using the service
tool).
The Request PGN message is also sensitive to the population of the
destination address field. When the engine #1 destination 00 is requested,
then the engine ECM responds with the RTS Transport protocol message,
and will not release the requested information until the handshake message
CTS is returned.
When the global destination is given for a Request PGN message FF
(Global), then the engine ECM responds by sending the requested message.
If the message is larger than 8 bytes then it will be released via the Transport
Protocol BAM message. When the global destination is used, there is no
need to use the RTS/CTS protocol.