For 1990-2009 cars

### MIL Operation

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 the 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

The PCM controlled lamps are intended to alert the driver to an operating condition which may require immediate attention. The instrument panel indicators, ignition 1 feed, powers the PCM controlled lamps.

#### Check Gauges Lamp

The PCM commands the Check Gauges lamp ON under the following conditions:

• | When the engine speed is greater than 1200 rpm and system voltage falls below 10 volts for longer than 10 seconds. The PCM commands the Check Gauges lamp OFF when system voltage rises to above 12 volts.

• | When the generator control circuit (L terminal) remains low for longer than 10 seconds.

• | When the engine speed is below 2000 rpm and the generator PWM control circuit (F terminal) duty cycle falls below 5% and remains below 15% for longer than 20 seconds.

• | When the engine speed is above 4000 rpm and the generator PWM control circuit (F terminal) duty cycle increases to above 95% and remains above 85% for longer than 20 seconds.