Chart A-2, "Service Engine Soon" Light Won't Go Out: Notes
The "SERVICE ENGINE SOON" light is attached to the IPC. It is powered by ignition "3" circuit No. 39. The ECM completes the ground to turn light on. The light will illuminate while engine is not running. With engine running, a steady light indicates an ECM code is set. When engine is running and diagnostics are entered, a flashing light indicates the field service mode of ECM. The system monitor button will not affect the "SERVICE ENGINE SOON" light.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- This step verifies that light remains on with engine running and no ECM codes displayed.
- Unplugging ECM harness connector (Yellow) determines if a short to ground exists in the ECM or somewhere else in circuit. If "SERVICE ENGINE SOON" light remains on, fault is not in ECM.
- This step removes the IPC to distinguish between a grounded IPC or a grounded circuit No. 419. If test light is illuminated when connected between IPC terminals "C9" and "D2" ("RBA" and "LT1" on Reatta and Riviera), circuit No. 419 is shorted to ground.