Circuit Description

A malfunction indicator lamp (MIL) lamp is illuminated by the powertrain control module (PCM) if diagnostics have detected certain errors related to the engine performance or engine sensor status. When the PCM is commanding the MIL ON, the voltage potential of the circuit will be low (near 0 volts). When the PCM is commanding the MIL OFF, the voltage potential of the circuit will be high (near battery voltage). The primary function of the PCM is to supply the ground for the MIL circuit.