Chart A-2, No DLC Data Or Won't Flash Code 12, Mil On Steady: Notes

Malfunction Indicator Light (MIL) should remain on when ignition switch is in ON position and engine is not running. Battery voltage is applied to indicator bulb. ECM controls indicator bulb and turns it on by providing a ground path through Purple wire to ECM.

With Data Link Connector (DLC) grounded, MIL should flash Code 12, followed by any fault code(s) stored in memory. A steady light indicates a short to ground in Purple wire or an open in Orange/Yellow wire.

1. If a problem in ECM is causing scan tester not to read serial data (DLC terminal No. 2), then ECM should not flash Code 12. If Code 12 does flash, ensure scan tester is working properly on another vehicle. If scan tester and Orange/Yellow wire are okay, ECM may be faulty.
2. If MIL goes off when ECM connector is disconnected, Purple wire is not shorted to ground.
3. Checks for open in Orange/Yellow wire.
4. MIL wiring is okay. Problem is a faulty ECM. If Code 12 does not flash, replace ECM.