VOLVO
ECM-841B - Autostarting, power supply. Signal too low
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)2006–2007Engine B5254T3 only
- Volvo S40 (2004–2013)2008Engine B5254T3, B5254T7 only
- Volvo S40 (2004–2013)2009–2012Engine B5254T7 only
- Volvo V50 (2004–2013)2006–2007Engine B5254T3 only
- Volvo V50 (2004–2013)2008–2012Engine B5254T7 only
What does this fault code mean?
The engine control module (ECM) measures the supply voltage when the engine is started. If the voltage stays below a certain level for a while, the control module treats it as a fault and sets the code. The fault mainly shows at starting, because the starter motor draws a lot of current from the battery. The code can therefore come from the battery or from poor connections in the starting circuit.
Possible causes
- The battery voltage is too low
- Raised contact resistance or oxidation in the connections
What you can do
- 1Check the condition of the battery and that the charging system works
- 2Check that the battery positive terminal and the earth connections are tight and free from oxidation
- 3Check the connections between the battery positive terminal, the start relay and the starter motor for contact resistance and oxidation
- 4Use a multimeter to confirm that voltage reaches the start relay when the start key is turned
- 5Repair as needed, clear the code and road test the car to see whether it comes back
Symptoms you may notice1
- The engine does not start
General guidance for car owners. Diagnosis on the car can point to a different cause.