VOLVO
ECM-0125 - Lambda probe signal. Faulty signal
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsS40 (1996–2004), V40 (1996–2004)
Show models by year and engine (2)
What does this fault code mean?
The front oxygen sensor is sending an incorrect signal to the engine control module. The fault is most often caused by poor contact, air entering the intake, or a break or short in the wiring, but the sensor itself may be defective.
Possible causes
- Contact resistance in the connections
- Signal wire shorted to ground
- Break in the signal wire, or the wire shorted to supply voltage
- Break in the ground wire, or the wire shorted to supply voltage
- Air leak in the intake system
- Defective front oxygen sensor
What you can do
- 1Switch the ignition off, then inspect the plugs at the control module and at the front oxygen sensor for poor contact and oxidation
- 2Check the intake system for air leaks, for example at hoses and connections
- 3Use a multimeter to check that the signal wire has no short to ground and does not break when you move the wiring
- 4If no wiring fault is found, have a workshop replace the front oxygen sensor
Symptoms you may notice1
- Malfunction indicator lamp (MIL) lights up
General guidance for car owners. Diagnosis on the car can point to a different cause.