General Information

NOTE: Graphics shown are only examples.

HINT: For general information about CAN-troubleshooting, see:

General about CAN-related diagnostic trouble codes.
CEM-DF01 - DF17 can only be stored in Central electronic module (CEM). These diagnostic trouble codes are stored when an electric fault is detected in CAN-lines. Start with these diagnostic trouble codes first.

CEM-1AXX only stored in Central electronic module (CEM). One diagnostic trouble code for every control module on the CAN-net. These diagnostic trouble codes indicate that Central electronic module (CEM) does not receive any reply from other control modules.

XXX-E000 (HS-CAN)/E001 (LS-CAN) can be stored in all CAN-connected control modules. These diagnostic trouble codes indicate that the control module has detected interference on the CAN-net.

XXX-E003 can be stored in all CAN-connected control modules except in Central electronic module (CEM). The control modules on the CAN-net listen for a message (identity number) that is sent out at regular intervals from Central electronic module (CEM). This diagnostic trouble code indicates that the control module has not received any identity number, or that the expected number is not correct. Interference on the CAN-net can also store this diagnostic trouble code.

NOTE: In case of CAN-related faults, it is likely that a combination of above diagnostic trouble codes occur.

NOTE: After fault with control modules that interfere with communication, other control modules may remain in Limp-Home (that is, they work with reduced functionality) even when the ignition has been turned off and on a few times. For certain faults in the CAN-net where control modules have stopped communicating, it may help to disconnect/reconnect the battery to "restart" the control module/CAN-net.

If a communication diagnostic trouble code can be read from the control module, the malfunction is probably intermittent.

Intermittent fault in the voltage supply and ground to a control module on the CAN network results in the Central electronic module (CEM) storing a diagnostic trouble code (DTC) for an open-circuit in communication with the control module where the voltage supply does not work. There will probably not be a diagnostic trouble code (DTC) in the control module where the open-circuit in the voltage supply occurred as the control module cannot store a diagnostic trouble code (DTC) when it is not supplied with power.

NOTE: Central electronic module (CEM) should not be replaced in case of CAN-fault, unless troubleshooting reveals that Central electronic module (CEM) has an internal fault.

CAUTION: During this fault-tracing use the wiring diagram to provide support when taking readings.

Fig 1: High-Speed CAN And Low-Speed CAN Communication Diagram
Courtesy of VOLVO CARS OF NORTH AMERICA.

Continue
Refer to Checking Resistance In CAN-Net