DTC Troubleshooting: P0720 (122)

DTC P0720:

Output Shaft (Countershaft) Speed Sensor Circuit Malfunction

1.	Start the engine. Hold the engine speed at 3,000 rpm (min-1) without load (in neutral) until the radiator fan comes on, then let it idle.

2.	Test-drive several minutes.

3.	Check the C SHAFT SPD in the DATA LIST with the HDS. Is any vehicle speed indicated? YES - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM.n NO - Go to 4.

4.	Turn the ignition switch OFF.

5.	Disconnect the output shaft (countershaft) speed sensor 3P connector.

6.	Turn the ignition switch ON (II).

7.	Measure voltage between output shaft (countershaft) speed sensor 3P connector terminal No. 1 and body ground.   Is there about 5 V? YES - Go to 8. NO - Repair open in the wire between the ECM (C13) and the output shaft (countershaft) speed sensor, then go to 18.

8.	Measure voltage between output shaft (countershaft) speed sensor 3P connector terminal No. 2 and body ground.   Is there about 5 V? YES - Go to 9. NO - Go to 10.

9.	Measure voltage between output shaft (countershaft) speed sensor 3P connector terminals No. 1 and No. 3.   Is there about 5 V? YES - Go to 16. NO - Repair open in the wire between the ECM (C14) and the output shaft (countershaft) speed sensor, then go to 18.

10.	Turn the ignition switch OFF.

11.	Jump the SCS line with the HDS.

12.	Disconnect ECM connector C (44P).

13.	Check for continuity between ECM connector terminal C43 and body ground.   Is there continuity? YES - Repair short in the wire between the ECM (C43) and the output shaft (countershaft) speed sensor, then go to 18. NO - Go to 14.

14.	Connect output shaft (countershaft) speed sensor 3P connector terminal No. 2 to body ground with a jumper wire.

15.	Check for continuity between ECM connector terminal C43 and body ground.   Is there continuity? YES - Go to 25. NO - Repair open in the wire between the ECM (C43) and the output shaft (countershaft) speed sensor, then go to 18.

16.	Turn the ignition switch OFF.

17.	Replace the output shaft (countershaft) speed sensor.

18.	Reconnect all connectors.

19.	Turn the ignition switch ON (II).

20.	Reset the ECM with the HDS.

21.	Do the ECM idle learn procedure.

22.	Test-drive under these conditions: ECT SENSOR 1 above 80 °C (176 °F) Transmission in 5th gear Engine speed between 2,000- 3,000 rpm (min-1) Drive for several minutes, then decelerate (with the throttle fully closed) for 8 seconds

23.

Check for Temporary DTCs or DTCs with the HDS. Are any Temporary DTCs or DTCs indicated? YES - If DTC P0720 is indicated, check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting. NO - Go to 24.

24.

Monitor the OBD STATUS for DTC P0720 in the DTCs MENU with the HDS. Does the screen indicate PASSED? YES - Troubleshooting is complete.n 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 1. If the screen indicates NOT COMPLETED, go to 22 and recheck.

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

26.	Test-drive under these conditions: ECT SENSOR 1 above 80 °C (176 °F) Transmission in 5th gear Engine speed between 2,000-3,000 rpm (min-1) Drive for several minutes, then decelerate (with the throttle fully closed) for 8 seconds

27.

Check for Temporary DTCs or DTCs with the HDS. Are any Temporary DTCs or DTCs indicated? YES - If DTC P0720 is indicated, check for poor connections or loose terminals at the output shaft (countershaft) speed sensor and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting. NO - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM.n