DTC Troubleshooting
DTC Troubleshooting: P0720
DTC P0720: Output Shaft (Countershaft) Speed Sensor Circuit Malfunction
NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information. Initial Inspection and Diagnostic Overview
1. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle.
2. Test-drive for several miles.
3. Check the C SHAFT SPD in the DATA LIST with the HDS.
Is any vehicle speed indicated?
YES - Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM.
NO - Go to step 4.
4. Turn the ignition switch to LOCK (0).
5. Disconnect the output shaft (countershaft) speed sensor 3P connector.
6. Turn the ignition switch to ON (II).
7. Measure the voltage between output shaft (countershaft) speed sensor 3P connector terminal No. 1 and body ground.
Is there about 5 V?
YES - Go to step 8.
NO - Repair open in the wire between the ECM (A20) and the output shaft (countershaft) speed sensor, then go to step 17.
8. Measure the voltage between output shaft (countershaft) speed sensor 3P connector terminal No. 2 and body ground.
Is there about 5 V?
YES - Go to step 9.
NO - Go to step 10.
9. Measure the voltage between output shaft (countershaft) speed sensor 3P connector terminals No. 1 and No. 3.
Is there about 5 V?
YES - Go to step 15.
NO - Repair open in the wire between the ECM (A23) and the output shaft (countershaft) speed sensor, then go to step 17.
10. Measure the voltage between ECM connector terminal A18 and body ground.
Is there about 5 V?
YES - Repair open in the wire between the ECM (A18) and the output shaft (countershaft) speed sensor, then go to step 17.
NO - Go to step 11.
11. Turn the ignition switch to LOCK (0).
12. Jump the SCS line with the HDS.
13. Disconnect ECM connector A (31P).
14. Check for continuity between ECM connector terminal A18 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (A18) and the output shaft (countershaft) speed sensor, then go to step 17.
NO - Go to step 24.
15. Turn the ignition switch to LOCK (0).
16. Replace the output shaft (countershaft) speed sensor. Service and Repair
17. Reconnect all connectors.
18. Turn the ignition switch to ON (II).
19. Reset the ECM with the HDS.
20. Do the ECM idle learn procedure. ECM Idle Learn Procedure
21. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in 5th
- Engine speed at 2,000-3,000 rpm
- Drive for several minutes, then decelerate (with the throttle fully closed) for 8 seconds
22. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0720 indicated?
YES - Check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM, then go to step 1.
NO - Go to step 23.
23. Monitor the OBD STATUS for DTC P0720 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 22, go to the indicated DTC's troubleshooting.
NO - If the screen indicates FAILED, check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM, then go to step 1. If the screen indicates NOT COMPLETED, go to step 21.
24. Reconnect all connectors.
25. Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM. Initial Inspection and Diagnostic Overview
26. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in 5th
- Engine speed at 2,000-3,000 rpm
- Drive for several minutes, then decelerate (with the throttle fully closed) for 8 seconds
27. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0720 indicated?
YES - Check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM.
NO - Go to step 28.
28. Monitor the OBD STATUS for DTC P0720 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. Service and Repair If any other Temporary DTCs or DTCs were indicated in step 27, go to the indicated DTC's troubleshooting.
NO - If the screen indicates FAILED, check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM. If the ECM was updated, substitute a known-good ECM, Initial Inspection and Diagnostic Overview then go to step 26. If the ECM was substituted, go to step 1. If the screen indicates NOT COMPLETED, go to step 26.