Alternator Lamp/Indicator: Description and Operation

GENERATOR LAMP-PCM OUTPUT
If the Powertrain Control Module (PCM) senses a low charging condition in the charging system, it will illuminate the generator lamp (if equipped) on the instrument panel. This is done through the CCD Bus circuits. For example, during low idle with all accessories turned on, the lamp may momentarily go on. Once the PCM corrects idle speed to a higher rpm, the lamp will go out.