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 DTCS



Are there any Transmission Control Relay, Line Pressure, and/or Loss of Prime DTCs present?

Yes


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


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



Is the DTC P2704 present also?

Yes


No
  • Go To 5

5.CHECK 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

6.CHECK IF DTC EVENT DATA WAS SET IN PARK, NEUTRAL OR REVERSE



Did the DTC P0876 set in Park, Neutral, or Reverse?

Yes


No
  • Go To 7

7.CHECK FOR UD PRESSURE SWITCH STATUS



Did the DTC P0876 set with the UD Pressure Switch closed?

Yes


No
  • Go To 8

8.CHECK 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








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


No

10.CHECK THE TCM AND WIRING



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.







Did the state of the UD Pressure Switch change while pressing the Pressure Switch Test button?

Yes


No

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








Is the resistance above 5.0 ohms?

Yes


No

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





Is the resistance below 5.0 ohms?

Yes


No

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




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




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


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



Did the state of the UD Pressure Switch change while pressing the Pressure Switch Test button?

Yes


No

15.CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY







Is the resistance below 5.0 ohms?

Yes


No

16.CHECK IF THE DTC RESETS





Does the DTC P0876 reset?

Yes


No

17.CHECK FOR A CUT NO. 2 CHECK BALL




Is the No. 2 check ball cut or damaged?

Yes


No

18.CHECK WIRING AND CONNECTORS






Were there any problems found?

Yes


No
  • Test Complete.