VOLVO
ECM-A20B - Engine control module (ECM). Signal missing
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
4 modelsC30 (2007–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)
Show models by year and engine (9)
- Volvo C30 (2007–2013)2007Engine B5254T3 only
- Volvo C30 (2007–2013)2008–2013Engine B5254T7 only
- Volvo C70 (2006–2013)2006–2007Engine B5254T3 only
- Volvo C70 (2006–2013)2008–2013Engine B5254T7 only
- Volvo S40 (2004–2013)2005–2007Engine B5254T3 only
- Volvo S40 (2004–2013)2008Engine B5254T3, B5254T7 only
- Volvo S40 (2004–2013)2009–2012Engine B5254T7 only
- Volvo V50 (2004–2013)2005–2007Engine B5254T3 only
- Volvo V50 (2004–2013)2008–2012Engine B5254T7 only
What does this fault code mean?
The central electronic module (CEM) sends a timer value over the CAN network that tells the modules how long the engine has been off since its last shutdown. The engine control module uses it, for example, when restarting a warm engine. The code is set when the engine control module finds the timer value wrong or missing, and the malfunction indicator lamp comes on.
Possible causes
- Fault in the central electronic module (CEM), which should be checked first
- Open or short circuit in the CAN wiring between the engine control module and the CEM
- Damaged central electronic module (CEM)
What you can do
- 1Read the fault codes in the CEM and in any other modules that may be involved, and note which are stored
- 2Remedy the faults in the CEM and the CAN network first; this code must not be cleared until the codes in the CEM and other affected modules are remedied and cleared
- 3Check the CAN wiring and connectors between the engine control module and the CEM for open circuits, short circuits and chafing
- 4After the repair, clear the code and start the car to see whether it returns
Symptoms you may notice1
- Malfunction indicator lamp (MIL) on
What the fault can affect1
- The engine control module calculates a timer value instead
General guidance for car owners. Diagnosis on the car can point to a different cause.