VOLVO
ECM-305C - Knock control. Internal fault
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 control module has recorded an internal fault in its own knock control circuit, so the fault is not in any sensor or in the wiring. It may be a single occurrence or a fault that is still present. The engine warning lamp may come on, and ignition timing is pulled back to protect the engine until the control module is repaired.
Possible causes
- Damaged control module
What you can do
- 1Clear the fault code, drive the car briefly and see whether the code returns
- 2Check the battery condition and that the cables and ground connections are secure, since interference at start-up can cause temporary faults
- 3Have a workshop replace the control module if the fault returns or remains
Symptoms you may notice2
- Poor performance
- Engine warning lamp lit
What the fault can affect1
- Ignition advance is pulled back to protect the engine
General guidance for car owners. Diagnosis on the car can point to a different cause.