P0876-UD PRESSURE SWITCH RATIONALITY
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The Transmission system uses five pressure switches to monitor the fluid pressure in the LR, 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.
| Possible Causes |
| RELATED RELAY DTC'S PRESENT |
| LOW FLUID LEVEL |
| NO. 2 CHECK BALL CUT OR DAMAGED |
| LOW LINE PRESSURE |
| CRACKED OR MISINSTALLED SUMP FILTER OR SEAL |
| STICKING MAIN REGULATOR VALVE IN PUMP VALVE BODY |
| (T29) UD PRESSURE SWITCH SENSE CIRCUIT OPEN |
| (T29) UD PRESSURE SWITCH CIRCUIT SHORT TO GROUND |
| (T29) UD PRESSURE SWITCH SENSE CIRCUIT SHORT TO ANOTHER CIRCUITS |
| TRANSMISSION SOLENOID/TRS ASSEMBLY |
| TRANSMISSION CONTROL MODULE |
Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
| GEAR | L/R | 2C | 4C | UD | OD |
| REVERSE | OPEN | OPEN | OPEN | OPEN | OPEN |
| P/N | CLOSED** | OPEN | OPEN | OPEN | OPEN |
| 1ST | CLOSED* | OPEN | OPEN | CLOSED | OPEN |
| 2ND | OPEN | CLOSED | OPEN | CLOSED | OPEN |
| 2ND PRIME | OPEN | OPEN | CLOSED | CLOSED | OPEN |
| 3RD | OPEN | OPEN | OPEN | CLOSED | CLOSED |
| 4TH | OPEN | OPEN | CLOSED | OPEN | CLOSED |
| 5TH | OPEN | CLOSED | OPEN | OPEN | CLOSED |
| *L/R is closed if output speed is below 100 rpm in Drive and Manual 2. L/R is closed in Manual 1. | |||||
| **May be open when rolling in Neutral or at low oil temperatures. | |||||
Diagnostic Test
1. CHECK FOR RELATED DTCSWith the scan tool, check for other transmission DTC's.
Are there any Transmission Control Relay, Line Pressure, and/or Loss of Prime DTCs present?
Yes
- Refer to the Transmission category and perform the appropriate symptom. If a Loss of Prime DTC is present, perform its respective test first. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - DIAGNOSIS AND TESTING)
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 DTC EVENT DATA.
NOTE: Make sure to record all DTC EVENT DATA stored in the scan tool for future reference in this test procedure.
Does the DTC EVENT DATA show all pressure switches reading CLOSED?
Yes
- Refer to the symptom category and perform diagnostics for P0882. Diagnose the symptom as if the DTC is current.
No
- Go To 4
4. CHECK FOR OTHER DTCS
With the scan tool, check for other transmission DTC's.
Is the DTC P2704 present also?
Yes
- Replace the Transmission Solenoid/TRS Assembly per the Service Information.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Go To 5
5. CHECK DTC EVENT DATA
With the scan tool, read and record the DTC EVENT DATA.
NOTE: Make sure to record all DTC EVENT DATA stored in the scan tool for future reference in this test procedure.
Does the DTC EVENT DATA display information for the DTC P0876?
Yes
- Go To 6
No
- Refer to the symptom list and perform diagnostics for the DTC listed in the DTC EVENT DATA.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
6. CHECK IF DTC EVENT DATA WAS SET IN PARK, NEUTRAL OR REVERSE
Refer to the DTC 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
Refer to the DTC 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 DTC EVENT DATA recorded earlier, compare the Line Pressure and the Desired Line Pressure.
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. Refer to the Service Information for the above procedures.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Go To 9
9. CHECK THE (T29) UD PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT
Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the Transmission Solenoid/TRS Assembly harness connector.
Measure the resistance between the (T29) UD Pressure Switch Sense 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 Switch Sense circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?
Yes
- Repair the (T29) UD Pressure Switch Sense circuit for a short to another circuit(s).
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Replace the Transmission Solenoid/TRS Assembly per the Service Information.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
10. CHECK THE TCM 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 SWITCH SENSE CIRCUIT FOR AN OPEN
Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333.
Disconnect the TCM harness connector.
Measure the resistance of the (T29) UD Pressure Switch Sense circuit from the Transmission Solenoid/TRS Assembly harness connector and the appropriate terminal of the TCM harness connector.
Is the resistance above 5.0 ohms?
Yes
- Repair the (T29) UD Pressure Switch Sense circuit for an open.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Go To 12
12. CHECK THE (T29) UD PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND
Measure the resistance between ground and the (T29) UD Pressure Switch Sense circuit.
Is the resistance below 5.0 ohms?
Yes
- Repair the (T29) UD Pressure Switch Sense circuit for a short to ground.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Go To 13
13. CHECK THE (T29) UD PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT
Disconnect the TCM harness connector.
NOTE: Make sure the Transmission Solenoid/TRS Assembly harness connector is disconnected.
Measure the resistance between the (T29) UD Pressure Switch Sense 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 Switch Sense circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?
Yes
- Repair the (T29) UD Pressure Switch Sense circuit for a short to another circuit(s).
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM per the Service Information. With the scan tool, perform QUICK LEARN.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
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 - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
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 TCM harness connector.
Measure the resistance between ground and the (T29) UD Pressure Switch Sense circuit in the TCM harness connector.
Is the resistance below 5.0 ohms?
Yes
- Replace the Transmission Solenoid/TRS Assembly per the Service Information.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
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 DTC 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 per the Service Information.
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 - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Replace the Transmission Solenoid/TRS Assembly per the Service Information. 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 - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
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 DTC 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 - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No
- Test Complete.