A Problem In Countershaft Speed Sensor Circuit

DTC P0720: A Problem in Countershaft Speed Sensor Circuit

NOTE: Record all freeze data and review General Troubleshooting Information before you troubleshoot.

1. Turn the ignition switch ON (II).
2. Check whether the OBD II scan tool indicates the code for the manifold absolute pressure (MAP) sensor.
Does the OBD II scan tool indicate the code for the MAP sensor?
YES - Perform the troubleshooting flowchart for the MAP sensor. Recheck for code P0720 after troubleshooting.
NO - Go to step 3.
Turn the ignition switch OFF.
4. Disconnect the countershaft speed sensor connector.
5. Turn the ignition switch ON (II).





6. Measure the voltage between the No. 1 terminal of the countershaft speed sensor connector and body ground.
Is there about 5 V ?
YES - Go to step 7.
NO - Go to step 15.
7. Turn the ignition switch OFF.
8. Disconnect PCM connector D (16P).





9. Check for continuity between the No. 2 terminal of the countershaft speed sensor connector and body ground.
Is there continuity?
YES - Repair short to ground in the wire between PCM connector terminal D10 and the countershaft speed sensor.
NO - Go to step 10.
10. Reconnect PCM connector D (16P).





11. Check for continuity between the No. 3 terminal of the countershaft speed sensor connector and body ground.
Is there continuity?
YES - Go to step 12.
NO - Repair open in the wire between PCM connector terminal D16 and the countershaft speed sensor.
12. Turn the ignition switch ON (II).





13. Measure the voltage between the No. 2 and No. 3 terminals of the countershaft speed sensor connector.
Is there about 5 V?
YES - Go to step 16.
NO - Go to step 14.





14. Measure the voltage between PCM connector terminals D10 and D16.
Is there about 5 V ?
YES - Repair open in the wire between PCM connector terminal D10 and the countershaft speed sensor.
NO - Check for loose terminal fit in the PCM connectors D10, D16 and C19. If necessary, substitute a known-good PCM and recheck.





15. Measure the voltage between PCM connector terminal C19 and body ground.
Is there 4.75 - 5.25 V?
YES - Repair open in the wire between PCM connector terminal C19 and the countershaft speed sensor connector.
NO - Check for loose terminal fit in the PCM connectors. If necessary, substitute a known-good PCM and recheck.
16. Connect the countershaft speed sensor connector.





17. Measure the voltage between PCM connector terminals D10 and D16.
Is there about 5 V or 0 V?
YES - Go to step 18.
NO - Replace the countershaft speed sensor.
18. Raise the front of the vehicle, and make sure it is securely supported.
19. Set the parking brake, and block both rear wheels securely.
20. Start the engine, then shift to the D5 position and drive the vehicle.





21. Measure the voltage between PCM connector terminals D10 and D16.
Is there 1.5 - 3.5 V?
YES - Check for loose terminal fit in the PCM connectors D10, D16 and C19. If necessary, substitute a known-good PCM and recheck.
NO - Replace the countershaft speed sensor.