VOLVO
ECM-0651 - Reference voltage B. Faulty signal
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
3 modelsC30 (2007–2013), S40 (2004–2013), V50 (2004–2013)
What does this fault code mean?
The ECM monitors reference voltage B, which goes to several components, and sets the code when that voltage is unstable. The fault may lie in a component's signal wire, or in the control module's own supply of the reference voltage. The malfunction indicator lamp lights.
Possible causes
- Component signal wire shorted to battery voltage or reference voltage
- Open circuit in the signal wire, or a short to earth in it
- Internal fault in the control module's supply of reference voltage
What you can do
- 1Check the connectors to the affected components for looseness, contact resistance and oxidation
- 2Check the component's signal wire for breaks and chafing
- 3With the ignition off, use a multimeter to check that the signal wire has no short to earth or to voltage
- 4If this does not remedy the fault, a workshop should decide whether the engine control module needs replacing
Symptoms you may notice1
- Malfunction indicator lamp is on
General guidance for car owners. Diagnosis on the car can point to a different cause.