Circuit Description
WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
There should always be a steady malfunction indicator lamp (MIL) when the ignition switch is in the ON position and the engine is not running. System voltage is applied to the indicator bulb and the powertrain control module (PCM) provides a path to ground. Once the engine starts, the PCM turns the OFF the MIL. When an engine control system malfunction occurs, the PCM turns ON the MIL and a diagnostic trouble code is stored in memory.