P0988-4C 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 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, engine running, with the transmission in gear.

  • Set Condition:

    The DTC is set if the 4C Pressure Switch reads open or closed at the wrong time in a given gear .


Possible Causes
  
RELATED TCM POWER INPUT DTCS PRESENT
  
DTC P0871 ALSO PRESENT
  
LOSS OF 12 VOLT FEED
  
(T48) 4C PRESSURE SWITCH SENSE CIRCUIT OPEN
  
(T48) 4C PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
  
EXCESSIVE FLUID LEAKAGE IN THE 4C CLUTCH CIRCUIT
  
#5 CHECK BALL CUT OR DAMAGED
  
LOW LINE PRESSURE
  
TRANSMISSION SOLENOID/TRS ASSEMBLY
  
POWERTRAIN CONTROL MODULE
  
WIRING AND CONNECTORS
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - DIAGNOSIS AND TESTING) .


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 To2

2.DTC DATA SHOW CURRENT DTC



Does the DTC EVENT DATA show data for DTC P0988?

Yes
  • Go To3


No
  • Refer to the Transmission category and perform the appropriate symptom shown in the DTC EVENT DATA.

3.MULTIPLE DTCS PRESENT



Are there two or more related Pressure Switch Sense DTCs present in addition to P0988?

Yes
  • Go To4


No
  • Go To7

4.RELATED DTC PRESENT


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 for P0988?

Yes
  • Refer to Transmission category and perform diagnostics for the DTC P0888.


No
  • Go To 5

5.DTC EVENT DATA READ OPEN



Do all the pressure switches read OPEN?

Yes
  • Go To 6


No
  • Go To 7

6.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 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. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)


No

7.DTC P0871 ALSO PRESENT



Is the DTC P0871 also present?

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


No
  • Go To 8

8.EATX DTC EVENT DATA READ PARK REVERSE OR NEUTRAL


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 DTC set in Park, Neutral, or Reverse for P0988?

Yes


No
  • Go To 9

9.EATX DTC EVENT DATA 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 the 4C Pressure Switch reading CLOSED?

Yes


No

10.PRIMARY OIL FILTER SEAL



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. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)


No

11.PCM 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 4C Pressure Switch change while pressing the Pressure Switch Test button?

Yes


No

12.TRANSMISSION SOLENOID/TRS ASSEMBLY




Where there any problems found?

Yes


No

13.(T48) 4C PRESSURE SWITCH SENSE CIRCUIT OPEN







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.




Is the resistance above 5.0 ohms?

Yes


No

14.(T48) 4C PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND





Is the resistance below 5.0 ohms?

Yes


No

15.#5 AND/OR #7 CHECK BALL CUT OR DAMAGED






Where there any problems found?

Yes


No

16.EXCESSIVE FLUID LEAKAGE WITH 4C CLUTCH CIRCUIT


NOTE: This hydraulic clutch circuit contains a small bleed orifice. Small leakage is considered normal.



Was there excessive air leakage in the 4C Clutch hydraulic circuit?

Yes


No