DTC Troubleshooting

DTC Troubleshooting: P0641

DTC P0641:

Sensor Reference Voltage A Malfunction

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information How To Troubleshoot The Fuel And Emissions Systems (Except FFV Model).

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

2. Clear the DTC with the HDS.

3. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?

YES -

Go to step 4.

NO -

Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the PCM and these parts:

- Input shaft (mainshaft) speed sensor
- APP sensor
- Throttle body
- EGR valve

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

5. Disconnect the connectors from these parts:

- Input shaft (mainshaft) speed sensor
- APP sensor
- Throttle body
- EGR valve

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

7. Clear the DTC with the HDS.

8. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?

YES -

Go to step 10.

NO -

Go to step 9.

9. Check for Pending or Confirmed DTCs with the HDS while reconnecting these parts, one at a time:

- Input shaft (mainshaft) speed sensor
- APP sensor
- Throttle body
- EGR valve

Is DTC P0641 indicated?

YES -

Replace the part that caused the DTC when it was reconnected, then go to step 14.

NO -

Check for poor connections or loose terminals at the PCM and the following parts, then go to step 1.

- Input shaft (mainshaft) speed sensor
- APP sensor
- Throttle body
- EGR valve

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

11. Jump the SCS line with the HDS.

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

13. Check for continuity between body ground and PCM connector terminals A24, B18, and C12 individually.













Is there continuity?

YES -

Repair a short in the wire between the PCM (A24, B18, or C12) and each part that was disconnected in step 5, then go to step 14.

NO -

Go to step 20.

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

15. Reconnect all connectors.

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

17. Reset the PCM with the HDS.

18. Do the PCM idle learn procedure PCM Idle Learn Procedure.

19. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?

YES -

Check for poor connections or loose terminals at the PCM and the following parts, then go to step 1.

- Input shaft (mainshaft) speed sensor
- APP sensor
- Throttle body
- EGR valve

NO -

Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.

20. Reconnect all connectors.

21. Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM.

22. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?

YES -

If the PCM was updated, substitute a known-good PCM, then recheck. If the PCM was substituted, check for poor connections or loose terminals at the PCM and the following parts, then go to step 1.

- Input shaft (mainshaft) speed sensor
- APP sensor
- Throttle body
- EGR valve

NO -

If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM PCM Replacement (Except FFV Model). If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.