37-1

VTM-4 DTC Troubleshooting: 37-1, 38-1

DTC 37-1, 38-1:

Engine Speed Signal Circuit Malfunction

NOTE: Before you troubleshoot, review the general troubleshooting information Initial Inspection and Diagnostic Overview.

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

2. Make sure the HDS communicates with the vehicle and the VTM-4 control unit. If it doesn't, troubleshoot the DLC circuit Testing and Inspection.

3. Clear the DTC with the HDS.

4. Test-drive the vehicle.

5. Check for DTCs with the HDS.

Is DTC 37-1 and/or 38-1 indicated?

YES -

Go to step 6.

NO -

Intermittent failure, the system is OK at this time.�

6. Check for DTCs in the PGM-FI system with the HDS.

Are there any PGM-FI DTC's indicated?

YES -

Go to the indicated DTC's troubleshooting.�

NO -

Go to step 7.

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

8. Disconnect VTM-4 control unit connector A (22P).

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

10. Measure the voltage between VTM-4 control unit connector terminal A12 and body ground.










Is the voltage correct?

YES -

Go to step 20.

NO -

Go to step 11.

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

12. Jump the SCS line with the HDS.

NOTE: This step must be done to prevent PCM damage.

13. Disconnect PCM connector A (49P).

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

15. Measure the voltage between VTM-4 control unit connector terminal A12 and body ground.





Is there voltage?

YES -

Repair a short to power in the wire between VTM-4 control unit connector terminal A12 and PCM connector terminal A33.�

NO -

Go to step 16.

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

17. Check for continuity between VTM-4 control unit connector terminal A12 and body ground.





Is there continuity?

YES -

Repair a short to ground in the wire between VTM-4 control unit connector terminal A12 and PCM connector terminal A33.�

NO -

Go to step 18.

18. Connect VTM-4 control unit connector terminal A12 and body ground with a jumper wire.






19. Check for continuity between PCM connector terminal A33 and body ground.





Is there continuity?

YES -

Go to step 20.

NO -

Repair an open in the wire between VTM-4 control unit connector terminal A12 and PCM connector terminal A33.�

20. Check for poor connections or loose terminals at the VTM-4 control unit connectors. If the connections are OK, substitute a known-good VTM-4 control unit Service and Repair, and recheck. If the symptom/indication goes away with the known-good VTM-4 control unit, replace the original VTM-4 control unit Service and Repair.

21. Test-drive the vehicle.

22. Check for DTCs with the HDS.

Is DTC 37-1 and/or 38-1 indicated?

YES -

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

NO -

Intermittent failure, the system is OK at this time.�