DTC Troubleshooting

Control System DTCs

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 How To Troubleshoot The Fuel And Emissions Systems.

1. Problem verification:

Problem verification
-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 several minutes.

-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 2.

2. Open wire check (VCC1 line):

Open wire check (VCC1 line)
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Turn the ignition switch to ON (II).

-4. Measure the voltage between test points 1 and 2.









Is there about 5.0 V?
-YES- The VCC1 wire is OK. Go to step 3.
-NO- Repair an open in the VCC1 wire between the output shaft (countershaft) speed sensor 3P connector and the ECM (C23), then do the repair verification.

3. Determine possible failure area (NC line, others):

Determine possible failure area (NC line, others)
-1. Measure the voltage between test points 1 and 2.









Is there about 5.0 V?
-YES- Go to step 4.
-NO- Go to step 5.

4. Open wire check (SG1 line):

Open wire check (SG1 line)
-1. Measure the voltage between test points 1 and 2.









Is there about 5.0 V?
-YES- The SG1 wire is OK. Replace the output shaft (countershaft) speed sensor Service and Repair, then do the repair verification.
-NO- Repair open in the SG1 wire between the ECM (C24) and the output shaft (countershaft) speed sensor, then do the repair verification.

5. Shorted wire check (NC line):

Shorted wire check (NC line)
-1. Turn the ignition switch to LOCK (0).

-2. Jump the SCS line with the HDS.

-3. Disconnect the following connector.





-4. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- Repair a short in the NC wire between the rocker arm oil pressure switch and the ECM (B48), then do the repair verification.
-NO- The NC wire is not shorted. Go to step 6.

6. Open wire check (NC line):

Open wire check (NC line)
-1. Measure the voltage between test points 1 and 2.









Is there continuity?
-YES- The NC wire is OK. Update the ECM ECM/PCM Update if it does not have the latest software, or substitute a known-good ECM Service and Repair, then do the repair verification.
-NO- Repair open in the NC wire between the ECM (B48) and the output shaft (countershaft) speed sensor, then do the repair verification.

Repair verification:

-1. Reconnect all connectors.

-2. Turn the ignition switch to ON (II).

-3. Reset the ECM with the HDS. How To Troubleshoot The Fuel And Emissions Systems

-4. Do the ECM idle learn procedure. ECM/PCM Idle Learn Procedure

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

-6. Check for Pending or Confirmed 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. If the ECM was updated, substitute a known-good ECM Service and Repair, then recheck. If the ECM was substituted, go to step 1.
-NO- Troubleshooting is complete. If the ECM was substituted, replace the original ECM Service and Repair. Check for other DTC after this troubleshooting. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.