P0871-OD PRESSURE SWITCH RATIONALITY





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear. Normal operation will be experienced if no other codes are present. Transmission Control System will ignore the code. Limp-in condition will only occur if DTC P0871 is present with a DTC P0706.


  • When Monitored:

    Whenever the engine is running.

  • Set Condition:

    The DTC is set if one of the pressure switches are open or closed at the wrong time in a given gear. If the problem is identified for 3 successive key starts, the transmission will go into Limp-in mode and the MIL will turn on after 10 seconds of vehicle operation.


Possible Causes
  
RELATED TRANSMISSION RELAY DTCS PRESENT
  
LOSS OF PRIME DTC PRESENT
  
(T9) OD PRESSURE SWITCH SENSE CIRCUIT OPEN
  
(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
  
(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE
  
TRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLY
  
POWERTRAIN CONTROL MODULE
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - DIAGNOSIS AND TESTING).


PRESSURE SWITCH STATES

GEAR
  		L/R
  		2/4
  		OD
  
R
  		OPEN
  		OPEN
  		OPEN
  
P/N
  		CLOSED
  		OPEN
  		OPEN
  
1st
  		CLOSED
  		OPEN
  		OPEN
  
2nd
  		OPEN
  		CLOSED
  		OPEN
  
D
  		OPEN
  		OPEN
  		CLOSED
  
OD
  		OPEN
  		CLOSED
  		CLOSED
  



Diagnostic Test

1.DETERMINING IF RELATED TRANSMISSION RELAY DTCS ARE PRESENT



Are there any Transmission Control Relay DTCs present also?

Yes
  • Refer to the Transmission category and perform the appropriate diagnostic procedure.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.


No
  • Go To 2

2.CHECK FOR LOSS OF PRIME DTC



Is the DTC P0944 present also?

Yes
  • Refer to the Transmission category and perform the appropriate diagnostic procedure.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.


No
  • Go To 3

3.CHECK TO SEE IF P0841 IS CURRENT



Is the status Active for this DTC or is the STARTS SINCE SET counter 2 or less?

Yes
  • Go To 4


No

4.PCM AND WIRING



CAUTION: Removal of the Starter Relay is to prevent a Transmission NO RESPONSE condition and to disable the starter.



NOTE: Check connectors - Clean/repair as necessary.






Did the OD Pressure Switch state change?

Yes
  • Go To 8


No
  • Go To 5

5.(T9) OD PRESSURE SWITCH SENSE CIRCUIT OPEN






NOTE: Check connectors - Clean/repair as necessary.


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 Special Tool #8815 to perform diagnosis.




Is the resistance above 5.0 ohms?

Yes
  • Repair the (T9) OD Pressure Switch Sense circuit for an open.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.


No
  • Go To 6

6.(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND





Is the resistance below 5.0 ohms?

Yes
  • Repair the (T9) OD Pressure Switch Sense circuit for a short to ground.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.


No
  • Go To 7

7.(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE




NOTE: Check connectors - Clean/repair as necessary.






Is the voltage above 0.5 volts?

Yes
  • Repair the (T9) OD Pressure Switch Sense circuit for a short to voltage.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.


No
  • Go To 9

8.OD PRESSURE SWITCH


If there are no possible causes remaining, view repair.

Repair
  • Replace the Transmission Solenoid/Pressure Switch Assembly per the Service Information.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.

9.POWERTRAIN CONTROL MODULE



If there are no possible causes remaining, view repair.

Repair
  • Replace and program the Powertrain Control Module per the Service Information. With the scan tool perform QUICK LEARN.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.

10.INTERMITTENT WIRING AND CONNECTORS






Were there any problems found?

Yes
  • Repair as necessary.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST.


No
  • Test Complete.