Chart A-1 No Service Engine Soon Light

PFI Chart A-1:

Engine Control Lamp Circuit:

DESCRIPTION:

The "Service Engine Soon" (SES) lamp is powered through the IPC and grounded by the ECM pin A19 (A10 for 91 Allante) to illuminate. The SES telltale will bulb check at key "ON", is illuminated steadily during cranking, and is illuminated whenever a trouble code with service message is set.

NOTES ON CHART A-1:

1. If the SES telltale is inoperative and code B334 is current, then the ECM may not be powering up at key ON, may not be receiving full time power from the battery, or may be damaged due to electrical overload or water intrusion.

2. Checking for power to the IPC. If no other telltales light, the IPC may not be receiving power.

3. Checking for ECM receiving ignition signal.

4. Fault is most likely at the ECM connector or ECM. Before replacing the ECM, perform the ECM replacement check, Chart C-1.

NOTE ON INTERMITTENTS:

Turn the ignition ON and manipulate circuit 419 while observing the SES telltale. If the telltale flashes OFF, repair intermittent open in circuit 419.