P0720

DTC P0720: Problem in Countershaft Speed Sensor Circuit

NOTE: Record all freeze data 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 indicated MAP sensor. Recheck for code P0720 after troubleshooting.
NO - Go to step 3.
3. Turn the ignition switch OFF.
4. Disconnect PCM connector A (31P).





5. Check for continuity between PCM connector terminals A23 and body ground, and between A24 and body ground.
Is there continuity?
YES - Go to step 6.
NO - Repair open in the wires between PCM connector terminals A23 and ground(G101), between A24 and ground (G101), and repair poor ground (G101).
6. Connect PCM connector A (31 P).
7. Disconnect the countershaft speed sensor connector.
8. Turn the ignition switch ON (II).





9. Measure the voltage between the No. 1 terminal of the countershaft speed sensor connector.
Is there about 5 V?
YES - Go to step 10.
NO - Go to step 20.
10. Turn the ignition switch OFF.





11. 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 C15 and the countershaft speed sensor connector.
NO - Go to step 12.





12. Check for continuity between the No. 3 terminal of the countershaft speed sensor connector and body ground.
Is there continuity?
YES - Go to step 13.
NO - Repair open in the wire between the countershaft speed sensor connector and ground (G101).
13. Turn the ignition switch ON (II).





14. 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 15.
NO - Go to step 24.
15. Connect the countershaft speed sensor connector.





16. Measure the voltage between PCM connector terminals C15 and A23 or A24.
Is the voltage 0 V or about 5 V?
YES - Go to step 17.
NO - Replace the countershaft speed sensor.
17. Raise the front of the vehicle, make sure it is securely supported, and allow the front wheels to rotate freely.
18. Start the engine, then shift to D position and let the wheels rotate.





19. Measure the voltage between PCM connector terminals C15 and A23 or A24.
Is there 1.5 V - 3.5 V?
YES - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM.
NO - Replace the countershaft speed sensor.





20. Measure the voltage between PCM connector terminals A21 and A23 or A24.
Is there 4.75 V - 5.25 V?
YES - Repair open in the wire between PCM connector terminal A21 and the countershaft speed sensor connector.
NO - Go to step 21.
21. Turn the ignition switch OFF.
22. Disconnect PCM connector A (31P).





23. Check for continuity between PCM connector terminal A21 and body ground.
Is there continuity?
YES - Repair short to ground in the wire between PCM connector terminal A21 and the countershaft speed sensor connector.

NOTE: A short to ground on this circuit damages the PCM.

NO - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM.





24. Measure the voltage between PCM connector terminals C15 and A23 or A24.
Is there about 5 V?
YES - Repair open in the wire between PCM connector terminal C15 and the countershaft speed sensor connector.
NO - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM.