P0846-2/4 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. The 2/4 pressure switch monitors the fluid pressure to the 2/4 clutch to confirm proper operation of the 2/4 solenoid. If the 2/4 pressure switch is identified as closed in P or N, the code will immediately be set and normal operation will be allowed for that given key start. If the problem is identified for 3 successive ignition cycles, the transmission will go into Limp-in mode.


  • 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 CONTROL OUTPUT DTCS PRESENT
 
LOSS OF PRIME DTC PRESENT
 
(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT OPEN
 
(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
 
(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE
 
TRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLY
 
POWERTRAIN CONTROL MODULE
 


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


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 symptom.


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.


No
  • Go To 3

3.CHECK TO SEE IF P0846 IS CURRENT



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

Yes
  • Go To 4


No
  • Go To 8

4.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 2/4 Pressure Switch state change?

Yes


No
  • Go To 5

5.(T47) 2/4 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 tool #8815 to perform diagnosis.




Is the resistance above 5.0 ohms?

Yes


No
  • Go To 6

6.(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND





Is the resistance below 5.0 ohms?

Yes


No
  • Go To 7

7.(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE




NOTE: Check connectors - Clean/repair as necessary.






Is the voltage above 0.5 volts?

Yes


No
  • Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM per the Service Information. With the scan tool, perform QUICK LEARN
  • Perform 42RLE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

8.INTERMITTENT WIRING AND CONNECTORS






Were there any problems found?

Yes


No
  • Test Complete.