Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Check Engine Light: Notes
All vehicles are equipped with a CHECK ENGINE light, located on the instrument panel. Light comes on, as a bulb check, when ignition switch is turned to the ON position and engine is not running. Light should not flash at this time, and should go out when engine is started.
If CHECK ENGINE light remains on, or flashes, with engine running, the self-diagnostic system has detected a problem. If the problem goes away, light will go out after 10 seconds, but a fault code will be stored in ECM memory.
If an EGR failure occurs, and then system returns to normal operation, CHECK ENGINE light will remain on until ignition switch is turned off.
ECM uses CHECK ENGINE light to flash 2-digit codes stored in ECM memory. If no fault codes are stored in memory, Code 12 will be flashed, indicating system is working normally. If other codes exists, the lowest code will be flashed 3 times, followed by the next higher code, which will also be flashed 3 times. This process is continued until all codes have been displayed. If CHECK ENGINE light illuminates steadily, ECM may be faulty.
If vehicle is equipped with an Electronic Spark Advance (ESA) module (no vacuum advance) in the ignition system, Code 41 will not be stored in ECM memory. When an XFi model fails to start, crank the engine, then ground diagnostic switch terminal with the ignition on. Read stored codes from ECM memory.
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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