VOLVO
ECM-941C - Stop lamp switch. Faulty signal
System
Engine Control Module (ECM)
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:
7 modelsC30 (2007–2013), C70 (2006–2013), S40 (2004–2013), S60 (2001–2009), S80 (1999–2006), V50 (2004–2013), V70 (2000–2008)
Show models by year and engine (13)
- Volvo C30 (2007–2013)2007–2011Engine B5244S4 only
- Volvo C70 (2006–2013)2006All engines except: B5254T3
- Volvo C70 (2006–2013)2007–2010Engine B5244S4, B5244S5 only
- Volvo C70 (2006–2013)2011Engine B5244S4 only
- Volvo S40 (2004–2013)2004Engine B5244S4, B5244S5 only
- Volvo S40 (2004–2013)2005–2010Engine B5244S4, B5244S5, B5244S7 only
- Volvo S60 (2001–2009)2003–2006Engine B5244S, B5244S2, B5244S6 only
- Volvo S60 (2001–2009)2007–2009Engine B5244S, B5244S2 only
- Volvo S80 (1999–2006)2003–2006Engine B5244S, B5244S2 only
- Volvo V50 (2004–2013)2004Engine B5244S4, B5244S5 only
- Volvo V50 (2004–2013)2005–2010Engine B5244S4, B5244S5, B5244S7 only
- Volvo V70 (2000–2008)2003–2006Engine B5244S, B5244S2, B5244S6 only
- Volvo V70 (2000–2008)2007–2008Engine B5244S, B5244S2 only
What does this fault code mean?
The ECM checks the brake pedal position sensor signal against the brake light switch. The signal reaches the ECM over CAN from the brake control module (BCM). The code is set for values that are wrong, unreasonable or do not match. Although the code concerns the brake light switch, the fault may lie in the sensor or the BCM.
Possible causes
- Contact resistance in the connections to the brake position sensor
- Brake light switch incorrectly fitted
- Brake light switch incorrectly adjusted
- Damaged brake position sensor
- Contact resistance or oxidation at the brake light switch connections
- Short to ground or open circuit in the brake light switch wiring
What you can do
- 1If you have a diagnostic tool: activate the read-out of brake pedal position and switch status with the engine running. The switch should show OFF when untouched and ON when pressed
- 2Check that the brake light switch is correctly fitted and adjusted. It should be closed when the pedal is pressed
- 3Check the connectors at the brake position sensor, the brake light switch and the ECM for play, contact resistance and oxidation
- 4If the brake position sensor gives a wrong value, start fault tracing in the brake control module (BCM)
- 5The brake system is safety-critical. If the fault remains or the brake light stays on, have a workshop check it, and do not drive with a safety fault in the brakes
Symptoms you may notice2
- Cruise control does not function at all
- Brake light constantly on
What the fault can affect1
- Cruise control is switched off while the fault is active
General guidance for car owners. Diagnosis on the car can point to a different cause.