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Home >> Volvo >> 2004 >> XC70 >> Repair and Diagnosis (Single Page) >> Electrical >> Body Electrical >> Central Electronic Module (CEM) Diagnostic Trouble Codes (XC) - 2 Of 7 >> CEM-1A61: Communication With The Transmission Control Module (TCM). Signal Missing (Aw50/51 AWD; 2001) >> Signal missing >> Signal missing >> General information

General information

HINT: For general information about fault-tracing the control area network (CAN), see the linked document below. See  General information about fault-tracing in the CAN network 

In order to check the control area network (CAN) cables, the resistance in the network must be measured. The resistance between the two CAN cables, with the network connected, must be 60Ω in both the high speed network and the low speed network.

NOTE: Resistance will only be 60 Ω if the main artery of the CAN network is whole and the network is connected. If the main artery of the CAN network is split somewhere and a reading is taken between the CAN cables, resistance will be 120 Ω.

If diagnostic trouble codes (DTCs) can be read off from the relevant control module, the fault is probably intermittent. The locations that must be checked in the event of a fault in the low speed network are the junctions behind the central electronic module (CEM) and the audio module (AUM) as well as the cable harness behind the Audio module (AUM).

Intermittent fault in the current supply to the actual control module is indicated by the DTC in the Central electronic module (CEM) (CEM-1A5X or CEM-1A6X). There is probably no diagnostic trouble code (DTC) in the relevant control module as the control module cannot store a diagnostic trouble code (DTC) when it is without power.

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