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ECM/PCM Power and Ground Circuit Troubleshooting




ECM/PCM Power and Ground Circuit Troubleshooting

1. Check the No. B60 IGSW (50 A) fuse in the under-dash fuse/relay box.

Is the fuse OK?

YES -

Repair an open in the wire between the No. B60 IGSW (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. B60 IGSW (50 A) fuse and the under-dash fuse/relay box. Also replace the No. B60 IGSW (50 A) fuse.

2. Inspect the No. B39 IGP (15 A) fuse in the under-dash fuse/relay box.

Is the fuse OK?

YES -

Go to step 9.

NO -

Go to step 3.

3. Remove the blown No. B39 IGP (15 A) fuse from the under-dash fuse/relay box.

4. Open the fuse lid panel (A), then remove PGM-FI main relay 1 (B) from the under-dash fuse/relay box.






5. Check for continuity between body ground and PGM-FI main relay 1 4P connector terminals No. 2 and No. 4 individually.





Is there continuity?

YES -

Replace the under-dash fuse/relay box; USA models Under-Dash Fuse/Relay Box Removal and Installation (USA Models), Canada models Under-Dash Fuse/Relay Box Removal and Installation (Canada Models).

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. 1 and body ground.

- PGM-FI main relay 2
- ECM/PCM connector A (44P)
- Each injector 2P connector
- CMP sensor 3P connector
- CKP sensor 3P connector
- Electronic throttle control system (ETCS) control relay





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

YES -

Replace the part that made the short to body ground go away when disconnected. If the part is the ECM/PCM, update the ECM/PCM if it does not have the latest software ECM/PCM Update, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM Service and Repair. Also replace the No. 39 IGP (15 A) fuse.

NO -

Go to step 7.

7. Disconnect the connectors from these parts:

- PGM-FI main relay 2
- ECM/PCM connector A (44P)
- Injectors
- CMP sensor
- CKP sensor
- Electronic throttle control system (ETCS) control relay

8. Check for continuity between PGM-FI main relay 1 4P connector terminal No. 1 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. B39 IGP (15 A) fuse.

NO -

Replace PGM-FI main relay 1. Also replace the No. B39 IGP (15 A) fuse.

9. Inspect the No. B20 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.

Is the fuse OK?

YES -

Go to step 19.

NO -

Go to step 10.

10. Remove the blown No. B20 FUEL PUMP (15 A) fuse from the under-dash fuse/relay box.

11. Remove PGM-FI main relay 2 (A) from auxiliary under-hood relay box A.






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

Is PGM-FI main relay 2 OK?

YES -

Go to step 13.

NO -

Replace PGM-FI main relay 2. Also replace the No. B20 FUEL PUMP (15 A) fuse.

13. Check for continuity between auxiliary under-hood relay box A 17P connector terminal No. 1 (PGM-FI main relay 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 ECM/PCM connector C (44P).

16. Check for continuity between auxiliary under-hood relay box A 17P connector terminal No. 1 (PGM-FI main relay 2) and body ground.





Is there continuity?

YES -

Repair a short in the wire between the No. B20 FUEL PUMP (15 A) fuse and the ECM/PCM (C36), or PGM-FI main relay 2. Also replace the No. B20 FUEL PUMP (15 A) fuse.

NO -

Replace the No. B20 FUEL PUMP (15 A) fuse, and update the ECM/PCM if it does not have the latest software ECM/PCM Update, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM Service and Repair.

17. Disconnect the fuel tank unit 4P connector Fuel Tank Unit Removal/Installation.

18. Check for continuity between fuel tank unit 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. B20 FUEL PUMP (15 A) fuse.

NO -

Check the fuel pump, and replace it if needed Fuel Pump/Fuel Gauge Sending Unit Replacement. Also replace the No. B20FUEL PUMP (15 A) fuse.

19. Jump the SCS line with the HDS.

20. Disconnect ECM/PCM connectors A (44P) and C (44P).

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

22. Measure the voltage between ECM/PCM connector terminal C36 and body ground.





Is there battery voltage?

YES -

Go to step 23.

NO -

Repair an open in the wire between the No. B20 FUEL PUMP (15 A) fuse and the ECM/PCM (C36).

23. Measure the voltage between ECM/PCM connector terminal A6 and body ground.





Is there battery voltage?

YES -

Go to step 29.

NO -

Go to step 24.

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

25. Open the fuse lid panel (A), then remove PGM-FI main relay 1 (B) from the under-dash fuse/relay box.






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





Is there battery voltage?

YES -

Go to step 27.

NO -

Replace the under-dash fuse/relay box; USA models Under-Dash Fuse/Relay Box Removal and Installation (USA Models), Canada models Under-Dash Fuse/Relay Box Removal and Installation (Canada Models).

27. Connect PGM-FI main relay 1 4P connector terminal No. 3 to body ground with a jumper wire.






28. Check for continuity between ECM/PCM connector terminal A6 and body ground.





Is there continuity?

YES -

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

NO -

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

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

30. Open the fuse lid panel (A), then remove PGM-FI main relay 1 (B) from the under-dash fuse/relay box.






31. Measure the voltage between PGM-FI main relay 1 4P connector terminal No. 2 and body ground.





Is there battery voltage?

YES -

Go to step 32.

NO -

Replace the under-dash fuse/relay box; USA models Under-Dash Fuse/Relay Box Removal and Installation (USA Models), Canada models Under-Dash Fuse/Relay Box Removal and Installation (Canada Models).

32. Connect PGM-FI main relay 1 4P connector terminal No. 1 to body ground with a jumper wire.






33. Check for continuity between body ground and ECM/PCM connector terminals A8 and A43 individually.





Is there continuity?

YES -

Remove the jumper wire, then go to step 34.

NO -

Repair an open in the wire between the ECM/PCM (A8, A43) and PGM-FI main relay 1.

34. Disconnect ECM/PCM connector B (44P).

35. Check for continuity between body ground and ECM/PCM connector terminals B1, B36, C2, C40, and C44 individually.









Is there continuity?

YES -

Go to step 36.

NO -

Repair an open in the wire between the ECM/PCM (B1, B36, C2, C40, C44) and G101; CVT, M/T.

36. Check for continuity between ECM/PCM connector terminal C39 and body ground.





Is there continuity?

YES -

Go to step 37.

NO -

Go to step 38.

37. Continue to check for continuity between ECM/PCM connector terminal C39 and body ground, while disconnecting these connectors, one at a time:

- MAP sensor 3P connector
- Output shaft (countershaft) speed sensor 3P connector (M/T)
- CVT output shaft (driven pulley) speed sensor 3P connector (CVT)

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

YES -

Replace the part that made the short to body ground go away when disconnected.

NO -

Repair a short in the wire between the ECM/PCM(C39) and the MAP sensor, the output shaft (countershaft) speed sensor (M/T), or the CVT output shaft (driven pulley) speed sensor (CVT).

38. Check for continuity between ECM/PCM connector terminal B6 and body ground.





Is there continuity?

YES -

Go to step 39.

NO -

Go to step 40.

39. Continue to check for continuity between ECM/PCM connector terminal C39 and body ground, while disconnecting these connectors, one at a time:

- EGR valve 5P connector
- CVT input shaft (drive pulley) speed sensor 3P connector (CVT)
- Vehicle speed sensor 3P connector (CVT)

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

YES -

Replace the part that made the short to body ground go away when disconnected.

NO -

Repair a short in the wire between the ECM/PCM (B6) and the EGR valve, the CVT input shaft (drive pulley) speed sensor (CVT), or the vehicle speed sensor (CVT).

40. Check for continuity between ECM/PCM connector terminal C12 and body ground.





Is there continuity?

YES -

Go to step 41.

NO -

Go to step 42.

41. Continue to check for continuity between ECM/PCM connector terminal C12 and body ground, while disconnecting the throttle body 6P connector.

Is there continuity?

YES -

Repair a short in the wire between the ECM/PCM (C12) and the throttle body.

NO -

Replace the throttle body Removal and Replacement.

42. Check for continuity between ECM/PCM connector terminal A25 and body ground.





Is there continuity?

YES -

Go to step 43.

NO -

Go to step 44.

43. Continue to check for continuity between ECM/PCM connector terminal A25 and body ground, while disconnecting the APP sensor 6P connector.

Is there continuity?

YES -

Repair a short in the wire between the ECM/PCM (A25) and APP sensor A.

NO -

Replace the accelerator pedal module Service and Repair.

44. Check for continuity between ECM/PCM connector terminal A24 and body ground.





Is there continuity?

YES -

Go to step 45.

NO -

Go to step 46.

45. Continue to check for continuity between ECM/PCM connector terminal A24 and body ground, while disconnecting the APP sensor 6P connector.

Is there continuity?

YES -

Repair a short in the wire between the ECM/PCM (A24) and APP sensor B.

NO -

Replace the accelerator pedal module Service and Repair.

46. Check for continuity between ECM/PCM connector terminal A19 and body ground.





Is there continuity?

YES -

Go to step 47.

NO -

Update the ECM/PCM if it does not have the latest software ECM/PCM Update, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM Service and Repair.

47. Continue to check for continuity between ECM/PCM connector terminal A19 and body ground, while disconnecting these connectors, one at a time:

- FTP sensor 3P connector
- A/C pressure 3P connector
- Brake booster pressure sensor A 3P connector
- Brake booster pressure sensor B 3P connector

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

YES -

Replace the part that made the short to body ground go away when disconnected.

NO -

Repair a short in the wire between the ECM/PCM (A19) and the FTP sensor, the A/C pressure sensor, brake booster pressure sensor A, or brake booster pressure sensor B.

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