Circuit Description

There should be a steady Malfunction Indicator Light (MIL) when ignition switch is in RUN position, prior to starting the engine. Battery ignition voltage is supplied to MIL. Powertrain Control Module (PCM) will illuminate MIL by grounding the control circuit at the PCM. A steady MIL with the engine running suggests a short to ground in the MIL control circuit, or a Diagnostic Trouble Code (DTC) is stored.