VOLVO
ECM-1935 - Stop lamp switch. Faulty signal
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 (10)
- Volvo C30 (2007–2013)2007Engine D4204T only
- Volvo C30 (2007–2013)2008–2010Engine D4204T only · Transmission MMT6, MPS6 only
- Volvo C70 (2006–2013)2008Engine D4204T only
- Volvo C70 (2006–2013)2009–2010Engine D4204T only · Transmission MMT6, MPS6 only
- Volvo S40 (2004–2013)2004–2006Engine D4204T, D4204T2 only
- Volvo S40 (2004–2013)2007Engine D4204T only
- Volvo S40 (2004–2013)2008–2010Engine D4204T only · Transmission MMT6, MPS6 only
- Volvo V50 (2004–2013)2004–2006Engine D4204T, D4204T2 only
- Volvo V50 (2004–2013)2007Engine D4204T only
- Volvo V50 (2004–2013)2008–2010Engine D4204T only · Transmission MMT6, MPS6 only
What does this fault code mean?
The ECM verifies that the signals from the brake pedal sensor and the brake light switch are reliable. If a fault is registered in either circuit, or in the messages passing between the BCM and the ECM, the code is set. Cruise control is switched off while the fault is present.
Possible causes
- Fault in the brake control module (BCM)
- Play, contact resistance or oxidation in the connections between the engine control module and the brake light switch
- Open circuit in the power supply to the brake light switch
- Open circuit, or a short to ground or supply voltage, in the wire to the brake light switch
- Brake light switch fitted incorrectly
- Damaged brake light switch
What you can do
- 1Sort out fault codes in the BCM and the CEM first, then clear this code
- 2Check that the brake lights come on when the brake pedal is pressed and go off when it is released
- 3Check that the brake light switch is correctly mounted in its bracket and that its connector is clean and secure
- 4Use a multimeter to check that the signal wire to the brake light switch has no open circuit and is not short-circuited to ground or supply voltage
- 5If you have a diagnostic tool, follow the brake light switch state in live data while you press and release the brake pedal
- 6Have a workshop check the brake light switch and the brake system if the fault remains
Symptoms you may notice2
- Text message or warning symbol in the display
- Poor performance or lack of power when driving
What the fault can affect1
- Cruise control is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.