Chart A-1 No Service Engine Soon Light

Chart A-1 - No "Service Engine Soon" Light:

Wiring Diagram for Chart A-1 - No "Service Engine Soon" Light:

CHART A-1 - NO "SERVICE ENGINE SOON" LIGHT

Circuit Description:

The "Service Engine Soon" light is installed in the IPC. The light is powered by the Central Power Supply CKT 812 and the ECM completes the ground to turn it "ON". The light should be "ON" with the engine not running however, with the engine running a steady light indicates an ECM code is set. When the engine is running and diagnostics are entered a flashing light indicates the operating mode of the ECM.




Test Description: The following numbered steps correspond with the step numbers on diagnostic chart.

1. Verifies that the CPS is working, If the CPS is not working the CRT would not operate. Diagnosis for this condition is covered in Chart A2 - Loss of CPS 12 volts.

2. A code B336 being set indicates that the IPC is not receiving 12 volts from the CPS and therefore would be able to light the Service Engine Soon Light. See Diagnosis for code B336.

3. This step splits the circuit into two sections. A "SES" light on after grounding terminal "D" indicates the open is on the ECM side of the circuit. The "SES" light being off would indicate the fault is on the IPC side of the circuit.

4. If the test light did not light, the ECM is not powered up and CKT 439 or ECM connector must be repaired.

5. Checks to see if the open is in the ECM or CKT 439. If the light is turned on by supplying a ground to the ECM harness terminal "A5", the fault is poor terminal contact at terminal "A5" or faulty ECM.

6. Since the IPC has the capability of turning on the SERVICE ENGNE SOON without using CKT 419 as a ground path, it can be determined if the open condition exists in CKT 419 or if the bulb or IPC are fault.