MID 128 / 144, SID 231 SAE J1939
FMI 2 – Data erratic, intermittent or incorrect
Fault code explanation: Communication fault J1939
Fault indication: DCU: Engine warning in DCU display.
CIU: Flash code
Electrical fault: 6.5 (EMS)
Value fault: None (EMS)
Electrical fault: 6.4 (CIU)
Value fault: None (CIU)
Symptom: Engine can not be started or if engine is running it can only be stopped by
pushing the aux-stop.
Instruments and warning lamps stop working.
Conditions for fault code: CAN communication is missing.
Possible reason: • CAN H and CAN L short circuited to eachother.
CAN H or CAN L short circuited to battery negative on pin 3.
CAN L short circuited to power supply on pin 4.
• CAN H or CAN L short circuited to any of the J1708 links.
Suitable action: 1 Check all data links between DCU/CIU and EMS2.
2 Check the contact pressure in socket 51 and 55 in the engine connector
3 Check that the socket 11 and 12 in the CIU connector is undamaged.
A CAN H – Engine connector
CAN L – Engine connector
C Power supply, 0 V
D Power supply, input
G J1708A – Engine connector
H J1708B – Engine connector
Checking CAN bus cable page
a Engine connector
30-2 Fault Tracing
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