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 approximately 5 seconds when ignition is on. MIL will also illuminate when a system failure is detected; a corresponding trouble code will set in Electronic Control Module (ECM) memory.
ECM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, ECM will illuminate MIL (CHECK ENGINE light) on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code will be stored in ECM. To retrieve stored codes, see RETRIEVING CODES (NON-SCAN) or RETRIEVING CODES (SCAN TESTER). Malfunctions are recorded as hard failures or as intermittent failures.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.