Circuit Description and Diagnostic Chart

SYSTEM: Back Up Power Source Circuit

WIRING DIAGRAM





CIRCUIT DESCRIPTION
Battery positive voltage is supplied to terminal BATT of the engine control module (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 of the back up.
^ If OK, proceed to next circuit inspection shown in the matrix chart in Diagnosis by Symptom under "Powertrain Management Testing Procedures".
Testing and Inspection
^ If not OK check and replace ECM.