P0721
DTC P0721: Problem in Output Shaft (Countershaft) Speed Sensor CircuitNOTE:
^ Record all freeze data and review General Troubleshooting Information before you troubleshoot.
^ This code is caused by an electrical circuit problem and cannot be caused by a mechanical problem in the transmission.
1. Record all freeze data, and clear the DTC with the HDS.
2. Check for proper output shaft (countershaft) speed sensor installation.
3. Raise the vehicle, make sure it is securely supported, and allow all four wheels to rotate freely.
4. Start the engine, disable the VSA by pressing the VSA OFF button, run the vehicle in the D position with engine speed 2,000 rpm or higher for more than 10 seconds. Slow down and stop the wheels.
5. Monitor the OBD status for P0721 in the DTCs/Freeze Date in A/T Mode Menu for a pass/fail.
Does the result indicate FAILED?
YES - Go to step 6.
NO - If the tester indicates PASSED, intermittent failure, the system is OK at this time. Check for loose or poor connections at the PCM and output shaft (countershaft) speed sensor connectors. If the tester indicates NOT COMPLETED, return to step 4 and recheck.
6. Turn the ignition switch OFF.
7. Jump the SCS line with the HDS.
8. Disconnect PCM connectors B 44P), C (44P), and output shaft (countershaft) speed sensor connector.
9. Check for continuity between PCM connector terminals 543, C40, B36, and between B1 and body ground. Is there continuity?
YES - Go to step 10.
NO - Repair an open in the wires between PCM connector terminals B1, B36, B43, C40, and ground (G101, G102), or repair poor ground (G101, G102), then go to step 31.
10. Connect PCM connectors B (44P) and C (44P).
11. Turn the ignition switch ON (II).
12. Measure the voltage between output shaft (countershaft) speed sensor connector terminal No. 1 and body ground.
Is there about 5 V?
YES - Go to step 17.
NO - Go to step 13.
13. Turn the ignition switch OFF.
14. Disconnect PCM connector B (44P).
15. Check for continuity between PCM connector terminal B18 and output shaft (countershaft) speed sensor connector terminal No. 1.
Is there continuity?.
YES - Go to step 16.
NO - Repair an open in the wire between PCM connector terminal B18 and the output shaft (countershaft) speed sensor, then go to step 31.
16. Check for continuity between PCM connector terminal B18 and body ground.
Is there continuity?
YES - Repair a short to ground in the wire between PCM connector terminal B18 and the output shaft (countershaft) speed sensor, then go to step 31.
NO - Check for loose or poor connections at PCM connector terminal 31.
8. If the connection is OK, 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.
17. Turn the ignition switch OFF.
18. Disconnect PCM connector B (44P).
19. Check for continuity between output shaft (countershaft) speed sensor connector terminal No. 2 and body ground.
Is there continuity?
YES - Repair a short to ground in the wire between PCM connector terminal B40 and output shaft (countershaft) speed sensor connector, then go to step 31.
NO - Go to step 20.
20. Check for continuity between PCM connector terminal B33 and output shaft (countershaft) speed sensor connector terminal No. 3.
Is there continuity?
YES - Go to step 21.
NO - Repair an open in the wire between output shaft (countershaft) speed sensor connector and PCM connector terminal 833, then go to step 31.
21. Connect PCM connector B (44P).
22. Turn the ignition switch ON (II).
23. Measure the voltage between output shaft (countershaft) speed sensor connector terminals No. 2 and No. 3.
Is thereabout 5 V?
YES - Go to step 27.
NO - Go to step 24.
24. Turn the ignition switch OFF.
25. Disconnect PCM connector B (44P).
26. Check for continuity between PCM connector terminal B40 and output shaft (countershaft) speed sensor connector terminal No. 2.
Is there continuity?
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 - Repair an open in the wire between PCM connector terminal B40 and the output shaft (countershaft) speed sensor, then go to step 31.
27. Connect the output shaft (countershaft) speed sensor Connector.
28. Clear the DTC with the HDS.
29. Start the engine, disable the VSA by pressing the VSA OFF button, run the vehicle in the D position with engine speed 2,000 rpm or higher for more than 10 seconds. Stow down and stop the wheels.
30. Monitor the OBD status for P0721 in the DTCs/Freeze Data in A/T Mode Menu for a pass/fail.
Does the result indicate FAILED?
YES - Replace the output shaft (countershaft) speed sensor, then go to step 31.
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.
31. Clear the DTC with the HDS.
32. Test-drive the vehicle for several minutes under the same conditions as those indicated by the freeze data.
33. Monitor the OBD status for P0721 in the DTCs/Freeze Data in A/T Mode Menu for a pass/fail.
Does the result indicate PASSED?
YES - Troubleshooting is completed.
NO - Return to step 6 and recheck.