Checking the wiring

Fig 1: Identifying Ignition OFF

Courtesy of VOLVO CARS OF NORTH AMERICA.

Fig 2: Identifying Control Module Disconnected

Courtesy of VOLVO CARS OF NORTH AMERICA.

• Ignition off
• Disconnect connectors D and C from the central electronic module (CEM).

  The diagnostic trouble code (DTC) indicates that the communication between the light switch module (LSM), central electronic module (CEM) and combustion preheater module (CPM) is not working. This may be due to a fault in the signal cable between the control modules or a damaged communication device in one or all of the control modules.

  Check the signal cable. Check for a short-circuit to supply voltage. Check for a short-circuit to ground.

  Take readings between:

  • Central electronic module (CEM) terminal #D41 (#41) and light switch module (LSM) terminal #3
  • Central electronic module (CEM) terminal #C32 (#32) and combustion preheater module (CPM) terminal #6.

  Remedy as necessary.

  Other information 

  • See Connecting the breakout box
  • See Signal specification
  • See Location of components
  • See Switches lights, replacing
  • For cars manufactured up to w38 2001 inclusive, see Control module, engine coolant heater, replacing
  • For cars manufactured from w39 2001 inclusive, see Control module engine coolant heater, replacing .
  • See Contents

Was a fault detected? 

• YES 

  Refer to Verification 

• NO 

  Refer to Replacing the control module