Diagnostic Procedure

DTC 78 Fuel Pump Control Circuit

DIAGNOSTIC PROCEDURE

1. CHECK FUEL PUMP OPERATION.
- If OK proceed to step 2.
- If not OK proceed to step 3.

2. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN THE DATA LINK CONNECTOR (DLC1) AND FUEL PUMP ELECTRONIC CONTROL UNIT (ECU).
- If OK proceed to step 5.
- If not OK repair or replace harness or connector.

3. CHECK VOLTAGE OF TERMINAL "+B" OF DLC1.
- If OK proceed to step 4.
- If not OK check ECM power source circuit.

4. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN DLC1 AND FUEL PUMP.
- If OK repair or replace fuel pump.
- If not OK repair or replace harness or connector.

5. CHECK VOLTAGE OF TERMINAL "FPC".
- If OK replace fuel pump ECU.
- If not OK proceed to step 6.

6. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN ECM AND FUEL PUMP ECU.
- If OK proceed to step 7.
- If not OK repair or replace harness or connector.

7. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN ECM AND FUEL PUMP ECU.
- If OK check and replace ECM.
- If not OK repair or replace harness or connector.