VOLVO
CEM-DD20 - LIN-bus 2. Communication fault
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
Applies to the following models:
5 modelsS60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)
What does this fault code mean?
Communication on LIN bus 2 is blocked, so the central module cannot reach one of the connected control modules. The cause may be a short circuit in the LIN wires or a fault in another unit on the same part of the network. Depending on engine and equipment, the battery may discharge or the BLIS LED may stay off.
Possible causes
- Short circuit between the LIN wires
- Fault in another unit on the same LIN network
What you can do
- 1Switch the ignition on and check whether the BLIS LEDs flash three times when the system is activated. Note which side does not flash
- 2If only one side does not flash, have a workshop replace the control module on that side
- 3On cars with alternator control, use a multimeter to check that the signal wire to the alternator control module has no break and no contact with ground
- 4If both LEDs flash three times but the fault remains, have a workshop check the alternator control module
Symptoms you may notice3
- On some engines the battery electrolyte boils with the engine running
- The battery discharges
- On cars with BLIS the LED does not light
General guidance for car owners. Diagnosis on the car can point to a different cause.