Description and Diagnostic Procedure

SYSTEM: ECM Power Source Circuit


CIRCUIT DESCRIPTION



When the Ignition Switch is turned ON, battery voltage is applied to the terminal IGSW of the engine control module (ECM), and the main relay control circuit in the ECM sends a signal to the terminal M-REL of the ECM, switching on the main relay. This signal causes current to flow through the coil, closing the contacts of the main relay and supplying power to the terminals B+ and B1+ of the ECM.
If the ignition switch is turned OFF, the ECM continues to switch on the main relay for a maximum of 2 seconds for the initial setting of the idle air control valve.

DIAGNOSTIC PROCEDURE



1. CHECK VOLTAGE OF ECM POWER SOURCE.
-> If OK proceed to "Diagnosis By Symptom".
-> If not OK proceed to step 2.

2. CHECK CONTINUITY BETWEEN TERMINALS E1 AND BODY GROUND.
-> If OK proceed to step 3.
-> If not OK check and clean ground point repair or replace harness or connector.

3. CHECK VOLTAGE OF TERMINAL IGSW.
-> If OK proceed to step 6.
-> If not OK proceed to step 4.

4. CHECK FUSES "AM2" AND "IGN".
-> If OK proceed to step 5.
-> If not OK check for short in the harness and all the components connected to fuses "AM2" OR "IGN".

5. CHECK IGNITION SWITCH.
-> If OK check for open in harness or connector between battery and ECM.
-> If not OK replace ignition switch.

6. CHECK VOLTAGE OF TERMINAL M-REL.
-> If OK proceed to step 7.
-> If not OK check and replace ECM
.
7. CHECK "EFI No.1" FUSE.
-> If OK proceed to step 8.
-> If not OK check for short in the harness and all the components connected to "EFI No.1" fuse.

8. CHECK "EFI MAIN" RELAY.
-> If OK proceed to step 9.
-> If not OK replace EFI Main Relay.

9. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN TERMINAL M-REL AND BODY GROUND.
-> If OK check and repair harness or connector between "EFI No.1" fuse and battery.
-> If not OK repair or replace harness or connector.