Description and Diagnosis Procedure

SYSTEM: Back Up Power Source Circuit

CIRCUIT DESCRIPTION

ECM Backup Power Circuit:

Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is OFF for use by the diagnostic trouble code memory and air-fuel ratio adaptive control value memory, etc.

DIAGNOSTIC PROCEDURE
1. CHECK "EFI" FUSE.
- If OK proceed to step 2.
- If not OK check for short in all the harness and components connected to "EFI" fuse.

2. CHECK VOLTAGE OF TERMINAL "BATT".
- If OK proceed to step 3.
- If not OK check and repair harness or connector between battery, "EFI" fuse and ECM.

3. CHECK OPERATION FOR THE BACK UP.
- If OK proceed to "Diagnosis By Symptom".
- If not OK check and replace ECM.