Checking The Wiring

HINT: Check connector 54/9 for oxidation even if no heater is connected. 

Fig 1: Identifying Ignition OFF

Courtesy of VOLVO CARS CORPORATION

Fig 2: Disconnecting Connector

Courtesy of VOLVO CARS CORPORATION

• 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 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
  • -2004: SIGNAL SPECIFICATION
  • 2005-: SIGNAL SPECIFICATION
  • see LOCATION OF COMPONENTS
  • see SWITCHES LIGHTS, REPLACING
  • see CONTROL MODULE ENGINE COOLANT HEATER, REPLACING
  • see CHECKING WIRING AND TERMINALS

Was a fault detected? 

• YES 

  Refer to VERIFICATION 

• NO 

  Refer to REPLACING THE CONTROL MODULE