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P0876







P0876-UD PRESSURE SWITCH RATIONALITY





For a complete wiring diagram Consult Diagrams/Electrical

Theory of Operation

The Transmission system uses five pressure switches to monitor the fluid pressure in the L/R, 2C, 4C, UD, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown.

- When Monitored:
Continuously with the ignition on and engine running.

- Set Condition:
This DTC is set if the UD pressure switch is in the wrong state for the current gear. For example, this code would be set if the UD pressure switch remained off while the transmission was in second gear.





Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. Testing and Inspection





Diagnostic Test

1. CHECK FOR RELATED DTCS
With the scan tool, read DTCs.
Are there any TCM Power Input, Line Pressure, and/or Loss of Prime DTCs present?

Yes

- Diagnose and repair the DTC(s). If a Loss of Prime DTC is present, perform its respective test first.

No

- Go to 2

2. CHECK FOR PRESSURE SWITCH DTCS
Are there two or more other pressure switch rationality DTCs present in addition to P0876?

Yes

- Go to 3

No

- Go to 4

3. CHECK IF ALL PRESSURE SWITCHES READ CLOSED
With the scan tool, read and record all Event Data.

NOTE: Make sure to record all Event Data stored in the scan tool for future reference in this test procedure.

Does the Event Data show all pressure switches reading CLOSED?

Yes

- Diagnose and repair the DTC(s).

No

- Go to 4

4. CHECK FOR OTHER DTCS
With the scan tool, read DTCs.
Is the DTC P2704 present also?

Yes

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 5

5. CHECK THE EVENT DATA
In the Event Data recorded earlier, does the Event Data display information for the DTC P0876?

Yes

- Go to 6

No

- Diagnose and repair the DTC(s).

6. CHECK IF EVENT DATA WAS SET IN PARK, NEUTRAL OR REVERSE
In the Event Data recorded earlier, did the DTC P0876 set in Park, Neutral, or Reverse?

Yes

- Go to 10

No

- Go to 7

7. CHECK FOR UD PRESSURE SWITCH STATUS
In the Event Data recorded earlier, did the DTC P0876 set with the UD Pressure Switch closed?

Yes

- Go to 10

No

- Go to 8

8. CHECK LINE PRESSURE
In the Event Data recorded earlier, is the Line Pressure less than 40 psi, and significantly below the Desired Line Pressure?

Yes

- Repair as necessary to correct low line pressure. Check fluid level and adjust as necessary. If fluid level is OK, check the Primary Oil Filter seal for a split, crack, or improperly installed. If the filter and seal are OK, check the Main Regulator Valve in the Oil Pump.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 9

9. CHECK THE (T29) UD PRESSURE SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




Turn the ignition off to the lock position.
Disconnect all PCM harness connectors.
Disconnect the Transmission Solenoid/TRS Assembly harness connector.
Measure the resistance between the (T29) UD Pressure Signal circuit and all other circuits in the Transmission Solenoid/TRS Assembly harness connector.
Is the resistance below 5.0 ohms between the (T29) UD Pressure Signal circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes

- Repair the (T29) UD Pressure Signal circuit for a short to another circuit(s).
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

10. CHECK THE PCM AND WIRING
Turn the ignition off to the lock position.
Remove the Starter Relay.

CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.

WARNING: The Starter Relay must be removed from the PDC. Failure to do so can result in personal injury or death.

NOTE: Failure to remove the Starter Relay can cause a Transmission - No Response condition.

Install the Transmission Simulator, Miller tool #8333.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector switch to the UD position.
With the scan tool, monitor the UD Pressure Switch state while pressing the Pressure Switch Test button on the Transmission Simulator.
Did the state of the UD Pressure Switch change while pressing the Pressure Switch Test button?

Yes

- Go to 14

No

- Go to 11

11. CHECK THE (T29) UD PRESSURE SIGNAL CIRCUIT FOR AN OPEN




Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333.
Disconnect the PCM C4 harness connector and connect Miller tool #8815.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller tool #8815 to perform diagnosis.

Measure the resistance of the (T29) UD Pressure Signal circuit from the Transmission Solenoid/TRS Assembly harness connector and the appropriate terminal of the special tool #8815.
Is the resistance above 5.0 ohms?

Yes

- Repair the (T29) UD Pressure Signal circuit for an open.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 12

12. CHECK THE (T29) UD PRESSURE SIGNAL CIRCUIT FOR A SHORT TO GROUND




Measure the resistance between ground and the (T29) UD Pressure Signal circuit.
Is the resistance below 5.0 ohms?

Yes

- Repair the (T29) UD Pressure Signal circuit for a short to ground.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 13

13. CHECK THE (T29) UD PRESSURE SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




Disconnect all PCM harness connectors.

NOTE: Make sure the Transmission Solenoid/TRS Assembly harness connector is disconnected.

Measure the resistance between the (T29) UD Pressure Signal circuit and all other circuits in the Transmission Solenoid/TRS Assembly harness connector.
Is the resistance below 5.0 ohms between the (T29) UD Pressure Signal circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes

- Repair the (T29) UD Pressure Signal circuit for a short to another circuit(s).
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the PCM. With the scan tool, perform Quick Learn.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

14. WIGGLE TEST USING THE TRANSMISSION SIMULATOR
Perform the steps in the previous test while wiggling the wiring harness and connectors pertaining to the UD Pressure Switch.
Did the state of the UD Pressure Switch change while pressing the Pressure Switch Test button?

Yes

- Repair the wiring harness and/or connectors as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 15

15. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY




Disconnect the Transmission Simulator and reconnect the Transmission Solenoid/TRS Assembly harness connector.
Disconnect the PCM C4 harness connector and connect Miller tool #8815.
Measure the resistance between ground and the (T29) UD Pressure Signal circuit in the appropriate terminal of Miller tool #8815.
Is the resistance below 5.0 ohms?

Yes

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 16

16. CHECK IF THE DTC RESETS
Reconnect all previously disconnected connectors.
With the scan tool, erase all transmission DTCs.
Test drive the vehicle. Using the Event Data recorded earlier, try to duplicate the conditions in which the DTC originally set.
Does the DTC P0876 reset?

Yes

- Go to 17

No

- Go to 18

17. CHECK FOR A CUT NO. 2 CHECK BALL
Remove the Valve Body.
Check the No. 2 check ball for cuts or damage.
Is the No. 2 check ball cut or damaged?

Yes

- Replace the No. 2 check ball. Check for excessive clutch debris in the oil pan. If excessive debris is present, check the UD Clutch and repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly. Check for excessive clutch debris in the oil pan. If excessive debris is present, check the UD Clutch and repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

18. CHECK WIRING AND CONNECTORS
The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorted and open circuits.
With the scan tool, check the Event Data to help identify the conditions in which the DTC was set.
Were there any problems found?

Yes

- Repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Test Complete.

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