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)
When ignition is first turned on, MIL should come on to verify bulb and circuit operation, and then go off. The MIL is located on instrument panel.
The Powertrain Control Module (PCM) monitors several different engine control system circuits. If PCM detects a malfunction on a monitored circuit often enough to indicate a problem, a Diagnostic Trouble Code (DTC) will be stored in PCM memory. If malfunction is emission related, PCM will illuminate MIL. MIL will stay on continuously if PCM has entered limp-in mode or identified a failed emission component. MIL will remain on until DTC is erased.
MIL will either flash or remain on steady if PCM detects an active engine misfire. Excessive engine misfires result in increased catalyst temperature and cause an increase Hydrocarbon (HC) emissions. Severe misfires may cause catalyst damage.
PCM may reset (turn off) MIL if PCM does not detect the malfunction for 3 consecutive trips, except for misfire and fuel system monitors. For misfire and fuel system monitors, if PCM does not detect the malfunction while engine is operating within 375 RPM of and within 10 percent of load of operating condition when malfunction was first detected.
A trip is defined as the engine is started, an increase of 40°F (4°C) in engine coolant temperature exists after engine is started, and engine coolant temperature reaches at least 160°F (71°C). For additional information on engine misfire and fuel system monitor, see ON-BOARD DIAGNOSTICS.
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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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