1. Turn the ignition key to the "On" position, but do not start the engine.
2. Press and hold the reset button on the instrument cluster for five seconds.
2. The check engine light will turn off.
If the check engine light does not turn off, or if it comes back on after a short time, you will need to have your car diagnosed by a qualified mechanic.
Here are some possible causes of a check engine light in a Mercedes C240:
- Oxygen sensor failure
- Catalytic converter failure
- Emissions system leak
- Spark plug failure
- Ignition coil failure
- Fuel injector failure
- Mass air flow sensor failure
- Throttle position sensor failure
- Engine coolant temperature sensor failure
