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.
ECM Check CEL Doesn't Flash Code 12 Or Remains On
This check determines why the CEL remains on or does not flash Code 12. Since the CEL is remote from the ECM, it can recognize faulty ECM power or ECM.
- Checks for proper CEL signal (approximately battery voltage) at ALCL.
- Checks for 12 volts at ECM ignition feed terminals.
- Checks for good ECM ground. If ECM power and ground terminals are OK, check ECM-to-connecter terminal connections.
- When vehicle is started, ECM turns CEL off. Voltage at ALCL should drop below 6 volts.
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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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