1. Turn your Mountaineer to "ON" position without starting the engine.
2. Press and hold down the gas and brake pedal simultaneously for at least 10 seconds.
3. Release the brake and gas pedal, and then step on them again for another 10 seconds.
4. Repeat steps 2-3 for 4 more times, or until the check engine light turns off.
5. Start your Mountaineer and check if the check engine light is off.
If the check engine light does not turn off after following these steps, it is recommended that you take your Mountaineer to a qualified mechanic for a more thorough diagnosis and repair.
