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PCM Power And Ground Circuit Troubleshooting




PCM Power and Ground Circuit Troubleshooting

1. Check the No. A3-1 IG MAIN (50 A) fuse in the under-hood fuse/relay box.

Is the fuse OK?

YES -

Repair an open in the wire between the No. A3-1 IG MAIN (50 A) fuse and the ignition switch. If the wire is OK, go to step 2.

NO -

Repair a short in the wire between the No. A3-1 IG MAIN (50 A) fuse and the ignition switch. Also replace the No. A3-1 IG MAIN (50 A) fuse.

2. Inspect the No. A17 FI MAIN (15 A) fuse in the under-hood fuse/relay box.

Is the fuse OK?

YES -

Go to step 9.

NO -

Go to step 3.

3. Remove the blown No. A17 FI MAIN (15 A) fuse from the under-hood fuse/relay box.

4. Remove PGM-FI main relay 1 (A) from the under-hood fuse/relay box.






5. Check for continuity between body ground and PGM-FI main relay 1 4P connector terminals No. 1 and No. 3 individually.





Is there continuity?

YES -

Replace the under-hood fuse/relay box Under-Hood Fuse/Relay Box Removal and Installation. Also replace the No. A17 FI MAIN(15 A)fuse.

NO -

Go to step 6.

6. While disconnecting each of the parts or connectors below, one at a time, check for continuity between PGM-FI main relay 1 4P connector terminal No. 2 and body ground:

- PGM-FI main relay 2
- PCM connector B (49P)
- Each injector 2P connector
- CMP sensor 3P connector
- CKP sensor 3P connector
- MAF sensor/IAT sensor 5P connector
- Electronic throttle control system (ETCS) control relay





Does continuity go away when one of the above parts or connectors is disconnected?

YES -

Replace the part that made the short to body ground go away when disconnected. If the part is the PCM, update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM, then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM Service and Repair. Also replace the No. A17 FI MAIN (15 A)fuse.

NO -

Go to step 7.

7. Disconnect the connectors from these parts:

- PGM-FI main relay 2
- PCM connector B (49P)
- Injectors
- CMP sensor
- CKP sensor
- MAF sensor/IAT sensor
- Electronic throttle control system (ETCS) control relay

8. Check for continuity between PGM-FI main relay 1 4P connector terminal No. 2 and body ground.





Is there continuity?

YES -

Repair a short in the wire between PGM-FI main relay 1 and each part. Also replace the No. A17 FI MAIN (15 A) fuse.

NO -

Replace PGM-FI main relay 1. Also replace the No. A17 FI MAIN (15 A) fuse.

9. Inspect the No. B9 FUEL PUMP (20 A) fuse in the driver's under-dash fuse/relay box.

Is the fuse OK?

YES -

Go to step 21.

NO -

Go to step 10.

10. Remove the blown No. B9 FUEL PUMP (20 A) fuse from the driver's under-dash fuse/relay box.

11. Remove PGM-FI main relay 2 (A) from the driver's under-dash fuse/relay box.





12. Test PGM-FI main relay 2 Testing and Inspection.

Is the relay OK?

YES -

Go to step 13.

NO -

Replace PGM-FI main relay 2. Also replace the No. B9 FUEL PUMP (20 A) fuse.

13. Check for continuity between PGM-FI main relay 2 4P connector terminal No. 2 and body ground.





Is there continuity?

YES -

Go to step 14.

NO -

Go to step 17.

14. Jump the SCS line with the HDS.

15. Disconnect PCM connector B (49P).

16. Check for continuity between PCM connector terminal B42 and body ground.





Is there continuity?

YES -

Repair a short in the wire between the No. B9 FUEL PUMP (20 A) fuse and the PCM (B42), between the No. B9 FUEL PUMP (20 A) fuse and PGM-FI main relay 2, or between the No. B9 FUEL PUMP (20 A) fuse and the immobilizer control unit. Also replace the No. B9 FUEL PUMP (20 A) fuse.

NO -

Replace the No. B9 FUEL PUMP (20 A) fuse, and update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM, then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM Service and Repair.

17. Remove the rear seat cushion.

18. Remove the access panel from the floor; 2WD, 4WD.

19. Disconnect the fuel pump 4P connector.

20. Check for continuity between fuel pump 4P connector terminal No. 1 and body ground.





Is there continuity?

YES -

Repair a short in the wire between the fuel pump and PGM-FI main relay 2. Also replace the No. B9 FUEL PUMP (20 A) fuse.

NO -

Check the fuel pump, and replace it if needed Fuel Pump/Fuel Gauge Sending Unit Replacement. Also replace the No. B9FUEL PUMP(20 A) fuse.

21. Jump the SCS line with the HDS.

22. Disconnect PCM connectors A (49P) and B (49P).

23. Turn the ignition switch to ON (II).

24. Measure the voltage between PCM connector terminal B42 and body ground.





Is there battery voltage?

YES -

Go to step 25.

NO -

Repair an open in the wire between the No. B9 FUEL PUMP (20 A) fuse and the PCM (B42).

25. Measure the voltage between PCM connector terminal A6 and body ground.





Is there battery voltage?

YES -

Go to step 30.

NO -

Go to step 26.

26. Turn the ignition switch to LOCK (0).

27. Remove PGM-FI main relay 1 (A) from the under-hood fuse/relay box.






28. Measure the voltage between PGM-FI main relay 1 4P connector terminal No. 3 and body ground.





Is there battery voltage?

YES -

Go to step 29.

NO -

Replace the under-hood fuse/relay box Under-Hood Fuse/Relay Box Removal and Installation.

29. Check for continuity between PGM-FI main relay 1 4P connector terminal No. 4 and PCM connector terminal A6.





Is there continuity?

YES -

Test PGM-FI main relay 1 Testing and Inspection. If the relay is OK, update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM, then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM Service and Repair.

NO -

Repair an open in the wire between the PCM (A6) and PGM-FI main relay 1.

30. Turn the ignition switch to LOCK (0).

31. Remove PGM-FI main relay 1 (A) from the under-hood fuse/relay box.






32. Measure the voltage between PGM-FI main relay 1 4P connector terminal No. 1 and body ground.





Is there battery voltage?

YES -

Go to step 33.

NO -

Replace the under-hood fuse/relay box Under-Hood Fuse/Relay Box Removal and Installation.

33. Check for continuity between PGM-FI main relay 1 4P connector terminal No. 2 and PCM connector terminal B3.





Is there continuity?

YES -

Go to step 34.

NO -

Repair an open in the wire between the PCM (B3) and PGM-FI main relay 1.

34. Test PGM-FI main relay 1 Testing and Inspection.

Is PGM-FI main relay 1 OK?

YES -

Go to step 35.

NO -

Replace PGM-FI main relay 1.

35. Disconnect PCM connectors A (49P), B (49P), and C (49P).

36. Check for continuity between body ground and PCM connector terminals A41, B1, B40, B41, C1, and C41 individually.













Is there continuity?

YES -

Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM, then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM Service and Repair.

NO -

Repair an open in the wire(s) between the PCM (A41, B1, B40, B41, C1, C41) and body ground (G101) Engine Wire Harness.

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