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.
Malfunction Indicator Light (Mil): Notes
Vehicles are equipped with a Malfunction Indicator Light (MIL). As a bulb check, light will illuminate for about 5 seconds when ignition is turned on. The MIL will also illuminate when a system failure is detected, and a corresponding Diagnostic Trouble Code (DTC) will set in ECM memory.
The Electronic Control Module (ECM) is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, the ECM will illuminate the MIL on the instrument panel and a corresponding DTC will be stored in ECM. To retrieve stored DTC(s), see RETRIEVING CODES . Malfunctions are recorded as hard failures or as intermittent failures.
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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.