Description and Diagnostic Procedure

SYSTEM: Back Up Power Source Circuit

CIRCUIT DESCRIPTION



Battery 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 No.1" FUSE.
^ If OK proceed to step 2.
^ If not OK check for short in the harness and all the 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 No.1" fuse and ECM.

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