LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Volvo >> 2008 >> XC70 >> Repair and Diagnosis (Single Page) >> Electrical >> Body Electrical >> Can-Related Faults And Central Electronic Module (CEM) - Description And Operation >> Can Network >> Can-Related Faults And Central Electronic Module (CEM) -Description And Operation >> Can Communication, Fault-Tracing >> Fault-Tracing >> General Information
April 5, 2026: LEMON Manuals is launched! Read the announcement.

General Information

NOTE:

Illustrations shown are only examples.

For general information about CAN-troubleshooting:

General about CAN-related diagnostic trouble codes. 

CEM-U000100/CEM-U000111/CEM-U000112/CEM-U000188 (HS CAN)  or CEM-U001000/CEM-U001011/CEM-U001012/CEM-U001088 (MS-CAN)  is generated when an electrical fault is detected in the CAN cables. Start with these diagnostic trouble codes first.

CEM-U01XX00 - CEM-U02XX00  indicates that Central electronic module (CEM) does not get a reply from, or has lost communication with, some control module on the CAN-net.

XXX-U000100/XXX-U000188 (HS-CAN)  or XXX-U001000/XXX-U001088 (MS-CAN)  can be generated in all CAN-connected control modules. For emission-related faults, diagnostic trouble code XXX-U007300  may also be stored. These diagnostic trouble codes indicate that the control module has detected interference on the CAN-net or another communication fault.

XXX-U010000 - XXX-U029900  can be stored in all CAN-connected control modules. These diagnostic trouble codes indicate that the control module does not receive any reply from or has lost communication with any control module on the CAN-net.

XXX-U030000  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.

XXX-U04XXXX - XXX-U05XXXX  can be stored in all CAN-connected control modules. These diagnostic trouble codes (deviations may occur) indicate that the control module has received invalid data from another control module on the CAN-net. It may also indicate that the control module has, due to signal from another control module, limited its own functionality.

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.

Fig 1: Identifying CAN Network
GLL173707Courtesy of VOLVO CARS CORPORATION
scientia non olet · About LEMON Manuals