P0871-OD 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:

    The appropriate DTC is set if one of the pressure switches are open or closed at the wrong time in a given gear.


Possible Causes
  
RELATED TCM POWER INPUT DTCS PRESENT
  
LINE PRESSURE DTCS PRESENT
  
NO. 4 OR 6 CHECK BALL CUT OR DAMAGED
  
(T9) OD PRESSURE SWITCH SENSE CIRCUIT OPEN
  
(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
  
(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO OTHER CIRCUITS
  
LOW LINE PRESSURE
  
WIRING AND CONNECTORS
  
CUT OD/REV PISTON SEAL
  
BROKEN OR MISSING DO/REV PISTON BLEED ORIFICE
  
BROKEN REACTION SHAFT SUPPORT SEAL RING
  
POOR MACHINING ON PUMP VALVE BODY FACE
  
BROKEN OR MISSING DRIBBLER ORIFICE ASSEMBLY IN REACTION SHAFT SUPPORT
  
TRANSMISSION SOLENOID/TRS ASSEMBLY
  
CUT OD ACCUMULATOR PISTON SEAL
  
CRACKED OD ACCUMULATOR PISTON
  
BROKEN OR MISSING OD BLEED ORIFICE IN MAIN VALVE BODY
  
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.DETERMINE IF RELATED TCM POWER INPUT DTCS ARE PRESENT



Are there any TCM Power Input DTCs present also?

Yes
  • Refer to the Transmission category and perform the appropriate symptom.


No
  • Go To 2

2.CHECK FOR LINE PRESSURE DTCS



Are there any Line Pressure DTCs present?

Yes
  • Refer to the Transmission category and perform the appropriate symptom.


No
  • Go To 3

3.CHECK FOR OTHER PRESSURE SWITCH DTCS



Are there two or more other pressure switch rationality DTCs present in addition to P0871?

Yes
  • Go To 5


No
  • Go To 4

4.CHECK IF DTC IS CURRENT


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 data for P0871?

Yes
  • Go To 8


No

5.CHECK IF 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.



Do all the pressure switches read CLOSED in the DTC EVENT DATA?

Yes


No
  • Go To 6

6.CHECK IF PRESSURE SWITCHES READ OPEN



Do all the pressure switches read open?

Yes
  • Go To 7


No
  • Go To 8

7.CHECK FOR LOW 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 weal for a spit, crack , or improperly installed. If the filer 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.


No

8.CHECK IF IN DTC SET IN PARK, NEUTRAL, OR REVERSE



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 the OD Pressure Switch DTC set while in Park, Neutral, or Reverse?

Yes


No
  • Go To 9

9.CHECK IF THE OD PRESSURE SWITCH IS OPEN



Did the OD Pressure Switch read OPEN?

Yes


No

10.CHECK FOR LOW 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 the fluid level. Check the Primary Oil Filter seal for a split, crack, or improperly installed. Refer to the Service Information for the proper installation procedure. If the fluid level and filter are OK, check the Main Regulator Valve in the Oil Pump.
  • Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)


No

11.CHECK THE (T9) OD PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT






NOTE: Check connectors - Clean/repair as necessary.




Is the resistance below 5.0 ohms between the (T9) OD Pressure Switch Sense circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes


No

12.CHECK IF DTC RESETS





Does the DTC P0871 reset?

Yes


No

13.CHECK THE TRANSMISSION CONTROL MODULE




Is the transmission slipping while in Drive?

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.CHECK INTERNAL TRANSMISSION


NOTE: The OD/Rev piston contains a small bleed orifice, a small amount of leakage between the OD and Reverse hydraulic clutch circuits is considered normal.



Is there excessive air leakage in any clutch circuit?

Yes
  • Check the OD/Rev piston seals and bleed orifice, reaction shaft support seal rings, dribbler orifice assemblies in the reaction shaft support and for poor machine on the pump valve body faces. Refer to the Service Information.
  • Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1.


No

15.CHECK 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 OD Pressure Switch change from OPEN to CLOSED while pressing the Test button?

Yes


No

16.CHECK IF THE NO. 4 AND/OR NO. 6 CHECK BALL IS CUT OR DAMAGED





Is the No. 4 and/or No. 6 Check Ball cut or damaged?

Yes


No

17.TRANSMISSION SOLENOID/TRS ASSEMBLY


Did the DTC P0871 reset during the test drive in the previous step?

Yes


No

18.CHECK THE (T9) OD PRESSURE SWITCH SENSE CIRCUIT FOR AN OPEN








Is the resistance above 5.0 ohms?

Yes


No

19.CHECK THE (T9) OD PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND





Is the resistance below 5.0 ohms?

Yes


No

20.CHECK WIRING AND CONNECTORS



Were there any problems found

Yes


No

21.CHECK IF DTC RESETS





Does the DTC P0871 reset?

Yes
  • 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)


No

22.CHECK WIRING AND CONNECTORS






Where there any problems found?

Yes


No
  • Test Complete.