Using MIL
- Turn ignition on, but leave engine off. Using a small screwdriver, turn diagnostic mode selector on ECM fully clockwise. Wait at least 2 seconds, and then turn diagnostic mode selector fully counterclockwise. Mode II self-diagnostics will result, and MIL and Red LED inspection light will flash codes (if present).
- If engine is started at this stage, MIL and Red LED inspection light will display condition of air/fuel mixture, monitored by HO2S sensor, whether system is in closed or open loop.
NOTE:
Turn diagnostic mode selector fully counterclockwise whenever vehicle is in use. Switching modes is not possible when engine is running.