DTC Troubleshooting
DTC Troubleshooting: P0843 (25-4)
DTC P0843:
Open in Transmission Fluid Pressure Switch A (2nd clutch) Circuit, or Transmission Fluid Pressure Switch A (2nd clutch) Stuck OFF
NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot with the HDS, and review General Troubleshooting Information How To Troubleshoot The A/T System.
1. Turn the ignition switch to ON (II).
2. Clear the DTC with the HDS.
3. Start the engine, and warm it up to normal operating temperature (the radiator fan comes on).
4. Shift to 2 while pressing the brake pedal, and verify with the HDS in the A/T Data List that the Shift Control indicates 2nd.
5. Check the 2nd Pressure Switch signal with the HDS in the A/T Data List.
Is the 2nd Pressure Switch ON?
YES -
Go to step 6.
NO -
Go to step 8.
6. Test-drive the vehicle in 2nd gear in D for at least 2 seconds. Slow down, and stop the wheels.
7. Monitor the OBD STATUS for P0843 in the DTCs MENU with the HDS.
Does the HDS indicate FAILED?
YES -
Go to step 9.
NO -
If the HDS indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals between the transmission fluid pressure switch A (2nd clutch) and the PCM. If the HDS indicates NOT COMPLETED, go to step 4.
8. Measure the 2nd clutch pressure A/T Pressure Test.
Is the 2nd clutch pressure within the service limits?
YES -
Go to step 9.
NO -
Repair shift valves A, B, and C, and related hydraulic circuit, or replace the transmission, then go to step 25.
9. Turn the ignition switch to LOCK (0).
10. Disconnect the transmission fluid pressure switch A (2nd clutch) connector.
11. Turn the ignition switch to ON (II).
12. Measure the voltage between the transmission fluid pressure switch A (2nd clutch) connector terminal and body ground.
Is there about 5 V?
YES -
Replace the transmission fluid pressure switch A (2nd clutch) Transmission Fluid Pressure Switch A (2nd Clutch) Replacement, then go to step 22.
NO -
Go to step 13.
13. Turn the ignition switch to LOCK (0).
14. Jump the SCS line with the HDS.
15. Disconnect PCM connector C (49P).
16. Check for continuity between PCM connector terminal C27 and the transmission fluid pressure switch A (2nd clutch) connector terminal.
Is there continuity?
YES -
Go to step 17.
NO -
Repair an open in the wire between PCM connector terminal C27 and the transmission fluid pressure switch A (2nd clutch), then go to step 22.
17. Reconnect all connectors.
18. Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM.
19. Test-drive the vehicle in 2nd gear in D for at least 2 seconds, then press the accelerator pedal so that the transmission upshifts to 3rd gear, then 4th gear. Drive for at least 2 seconds in each gear. Slow down, and stop the wheels.
20. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0843 indicated?
YES -
If the PCM was updated, substitute a known-good PCM, then recheck. If the PCM was substituted, go to step 1.
NO -
Go to step 21.
21. Monitor the OBD STATUS for P0843 in the DTCs MENU with the HDS.
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 Pending or Confirmed DTCs were indicated in step 20, go to the indicated DTC's troubleshooting.�
NO -
If the HDS indicates FAILED, check for poor connections or loose terminals between the transmission fluid pressure switch A (2nd clutch) and the PCM. If the PCM was updated, substitute a known-good PCM, then recheck. If the PCM was substituted, go to step 1. If the HDS indicates NOT COMPLETED, go to step 19.
22. Reconnect all connectors.
23. Turn the ignition switch to ON (II).
24. Clear the DTC with the HDS.
25. Test-drive the vehicle in 2nd gear in D for at least 2 seconds, then press the accelerator pedal so that the transmission upshifts to 3rd gear, then 4th gear. Drive for at least 2 seconds in each gear. Slow down, and stop the wheels.
26. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0843 indicated?
YES -
Check for poor connections or loose terminals between the transmission fluid pressure switch A (2nd clutch) and the PCM, then go to step 1.
NO -
Go to step 27.
27. Monitor the OBD STATUS for P0843 in the DTCs MENU with the HDS.
Does the HDS indicate PASSED?
YES -
Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 26, go to the indicated DTC's troubleshooting.�
NO -
If the HDS indicates FAILED, check for poor connections or loose terminals between the transmission fluid pressure switch A (2nd clutch) and the PCM, then go to step 1. If the HDS indicates NOT COMPLETED, go to step 25.