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.
MIL Operation
1999 Chevrolet Lumina V6-3.8L VIN KSECTION MIL Operation
Malfunction Indicator Lamp
The PCM controlled lamps are intended to alert the driver to an operating condition which may require immediate attention. Ignition positive voltage powers the PCM controlled lamps. The PCM commands the lamps ON by applying ground to the lamp control circuit.
The Malfunction Indicator Lamp (MIL) is located on the instrument panel (CHECK ENGINE) or (SERVICE ENGINE SOON). The MIL performs the following functions:
^ It informs the driver that a problem has occurred and that the vehicle should be taken for service as soon as possible.
^ As a bulb check and system check, the MIL will illuminate with the ignition switch ON and the engine not running. when the engine is started, the MIL will turn OFF. If the MIL remains ON, the self-diagnostic system has detected a problem. If the problem goes away, the MIL will turn OFF in most cases, but a diagnostic trouble code will remain stored.
^ If the MIL is illuminated, then the engine stalls, the MIL will remain Illuminated so long as he ignition switch is ON.
^ Now, if the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.
Perform the Powertrain On-Board Diagnostic System Check first, when the following conditions are present:
^ When the MIL does not turn ON when the the ignition switch is turned to the RUN position
^ When the MIL remains ON while the engine is running
^ When you suspect a driveability problem
^ When you suspect an emissions problem
The PCM controlled lamps are intended to alert the driver to an operating condition which may require immediate attention. Ignition positive voltage powers the PCM controlled lamps. The PCM commands the lamps ON by applying ground to the lamp control circuit.
The Malfunction Indicator Lamp (MIL) is located on the instrument panel (CHECK ENGINE) or (SERVICE ENGINE SOON). The MIL performs the following functions:
^ It informs the driver that a problem has occurred and that the vehicle should be taken for service as soon as possible.
^ As a bulb check and system check, the MIL will illuminate with the ignition switch ON and the engine not running. when the engine is started, the MIL will turn OFF. If the MIL remains ON, the self-diagnostic system has detected a problem. If the problem goes away, the MIL will turn OFF in most cases, but a diagnostic trouble code will remain stored.
^ If the MIL is illuminated, then the engine stalls, the MIL will remain Illuminated so long as he ignition switch is ON.
^ Now, if the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.
Perform the Powertrain On-Board Diagnostic System Check first, when the following conditions are present:
^ When the MIL does not turn ON when the the ignition switch is turned to the RUN position
^ When the MIL remains ON while the engine is running
^ When you suspect a driveability problem
^ When you suspect an emissions problem
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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.