Malfunction Indicator Lamp: Description and Operation

CIRCUIT OPERATION
The Check Engine lamp (Malfunction Indicator Lamp) illuminates when the ignition switch is in the ON position and prior to starting the vehicle. The lamp will turn off after the vehicle is started.

If while the vehicle is running a problem is detected in the engine control system the lamp is illuminated. This is accomplished by the Powertrain Control Module (PCM) grounding the G3 circuit.

Power for the lamp is supplied on circuit G5. This circuit is protected by a 5 Amp fuse located in cavity 8 of the fuse block and is HOT in the START and RUN position only Power for the fuse is supplied on circuit A21 from the ignition switch.

Power for the A21 circuit is supplied on circuit A1. This circuit is protected by a fusible link located near the auxiliary jumper post on the left toe box.