DTC Troubleshooting

DTC Troubleshooting: P0873 (27)

DTC P0873: Open in 4th Clutch Transmission Fluid Pressure Switch Circuit, or 4th Clutch Transmission Fluid Pressure Switch Stuck OFF

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review General Troubleshooting Information. How to Troubleshoot A/T Systems

1. Clear the DTC with the HDS.

2. Start the engine, and warm it up to normal operating temperature (the radiator fan comes on).

3. Test-drive the vehicle in 5th gear in D, and verify with the HDS in the A/T Data List that the SHIFT COMMAND indicates 4th.

4. Check the 4th Pressure Switch signal with the HDS in the A/T Data List.

Is the 4th Pressure Switch ON?
YES - Go to step 5.

NO - Go to step 7.


5. Test-drive the vehicle in 4th gear in D for at least 2 seconds, then slow down to a stop.

6. Monitor the OBD status for P0873 in the DTCs/Freeze Data in A/T Mode Menu for a pass/fail.

Does the HDS indicate FAILED?
YES - Go to step 8.

NO - If the HDS indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals between the 4th clutch transmission fluid pressure switch and the PCM. If the HDS indicates NOT COMPLETED, go to step 5.


7. Measure the 4th clutch pressure. A/T Pressure Test

Is the 4th clutch pressure within the service limits?
YES - Go to step 8.

NO - Repair shift valves A, B, C, and D, and related hydraulic circuit, or replace the transmission, then go to step 23.


8. Turn the ignition switch to LOCK (0).

9. Disconnect the 4th clutch transmission fluid pressure switch connector.

10. Turn the ignition switch to ON (II).

11. Measure the voltage between the 4th clutch transmission fluid pressure switch connector terminal and body ground.

Is there about 5 V?
YES - Replace the 4th clutch transmission fluid pressure switch, 4th Clutch Transmission Fluid Pressure Switch Replacement then go to step 21.

NO - Go to step 12.






12. Turn the ignition switch to LOCK (0).

13. Jump the SCS line with the HDS.

14. Disconnect PCM connector C (49P).

15. Check for continuity between PCM connector terminal C37 and the 4th clutch transmission fluid pressure switch connector terminal.

Is there continuity?
YES - Go to step 16.

NO - Repair open in the wire between PCM connector terminal C37 and the 4th clutch transmission fluid pressure switch, then go to step 21.






16. Reconnect all connectors.

17. Update the A/T software in the PCM if it does not have the latest software, PCM Update or substitute a known-good PCM. Initial Inspection and Diagnostic Overview

18. Drive the vehicle in 3rd gear in D for at least 2 seconds, then press the accelerator pedal so that the transmission upshifts to 4th gear, and drive for at least 2 seconds. Slow down and stop the wheels.

19. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0873 indicated?
YES - If the PCM was updated, substitute a known-good PCM, Initial Inspection and Diagnostic Overview then recheck. If the PCM was substituted, go to step 1.

NO - Go to step 20.


20. Monitor the OBD status for P0873 in the DTCs/Freeze Data in A/T Mode Menu for a pass/fail.

Does the HDS indicate PASSED?
YES - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM. Service and Repair If any other DTCs were indicated on step 19, go to the indicated DTC's troubleshooting.

NO - If the HDS indicates FAILED, check for poor connections and loose terminals between the 4th clutch transmission fluid pressure switch and the PCM. If the PCM was updated, substitute a known-good PCM, Initial Inspection and Diagnostic Overview then recheck. If the PCM was substituted, go to step 1. If the HDS indicates NOT COMPLETED, go to step 18.


21. Reconnect all connectors.

22. Clear the DTC with the HDS.

23. Drive the vehicle in 3rd gear in D for at least 2 seconds, then press the accelerator pedal so that the transmission upshifts to 4th gear, and drive for at least 2 seconds. Slow down and stop the wheels.

24. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0873 indicated?
YES - Check for poor connections and loose terminals between the 4th clutch transmission fluid pressure switch and the PCM, then go to step 1.

NO - Go to step 25.


25. Monitor the OBD status for P0873 in the DTCs/Freeze Data in A/T Mode Menu for a pass/fail.

Does the HDS indicate PASSED?
YES - Troubleshooting is complete. If any other DTCs were indicated on step 24, go to the indicated DTC's troubleshooting.

NO - If the HDS indicates FAILED, check for poor connections and loose terminals between the 4th clutch transmission fluid pressure switch and the PCM, then go to step 1. If the HDS indicates NOT COMPLETED, go to step 23.