Powertrain Control Module (PCM)

The PCM controls the SERVICE ENGINE SOON telltale indicator lamp, (also called the Malfunction Indicator Lamp [MIL]), SERVICE (Wrench), coolant temp/low coolant/auto trans fluid temp, LOW FUEL telltale indicator lamps. It controls these telltale indicator lamps by pulling the control circuit to ground. When the circuit is pulled to ground, the telltale indicator lamp is turned On.

The PCM also supplies the speed signal input to the Integrated Circuit (IC), located in the instrument cluster, for control of the speedometer and odometer. The PCM receives a vehicle speed input from the vehicle speed sensor.

In addition the PCM also controls the tachometer, fuel gage, and coolant temperature gage based on inputs from the crankshaft position sensor, fuel level sensor, and engine coolant temperature sensor respectively. Refer to those gage descriptions for operation.