Jeep Liberty KJ. Manual — part 1025
P0846-2/4 PRESSURE SWITCH RATIONALITY
For a complete wiring diagram Refer to Section 8W.
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•
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)
Theory of Operation
The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD ele-
ments. 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 pres-
sure 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.
PRESSURE SWITCH STATES
GEAR
L/R
2/4
OD
R
OP
OP
OP
P/N
CL
OP
OP
1st
CL
OP
OP
2nd
OP
CL
OP
D
OP
OP
CL
OD
OP
CL
CL
OP = OPEN
CL = CLOSED
Diagnostic Test
1.
DETERMINING IF RELATED TRANSMISSION RELAY DTCS ARE PRESENT
With the scan tool, read Transmission DTCs
Are there any Transmission Control Relay DTCs present also?
Yes
>> Refer to the Transmission category and perform the appropriate symptom.
No
>> Go To 2
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AUTOMATIC TRANSMISSION 42RLE - ELECTRICAL DIAGNOSTICS
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2.
CHECK FOR LOSS OF PRIME DTC
With the scan tool, check for other Transmission DTCs.
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
With the scan tool, view DTCs.
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
Turn the ignition off to the lock position.
Remove the Starter Relay.
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.
Install the Transmission Simulator, Miller tool #8333 and the Electronic Transmission Adapter kit.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector to 2/4.
With the scan tool , monitor the 2/4 Pressure Switch state while pressing the Pressure Switch Test button on the
Transmission Simulator.
Did the 2/4 Pressure Switch state change?
Yes
>> Replace the Transmission Solenoid/Pressure Switch Assembly per the Service Information.
Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
No
>> Go To 5
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5.
(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT OPEN
Turn the ignition off to the lock position.
Disconnect the PCM C4 harness connector.
Disconnect the Transmission Solenoid/Pressure Switch Assembly har-
ness connector.
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 per-
form diagnosis.
Measure the resistance of the (T47) 2/4 Pressure Switch Sense circuit
from the appropriate terminal of special tool #8815 to the Transmission
Solenoid/Pressure Switch Assembly harness connector.
Is the resistance above 5.0 ohms?
Yes
>> Repair the (T47) 2/4 Pressure Switch Sense circuit for an
open.
Perform 42RLE TRANSMISSION VERIFICATION TEST -
VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AU-
TOMATIC - 42RLE - STANDARD PROCEDURE)
No
>> Go To 6
6.
(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
Measure the resistance between ground and the (T47) 2/4 Pressure
Switch Sense circuit.
Is the resistance below 5.0 ohms?
Yes
>> Repair the (T47) 2/4 Pressure Switch Sense circuit for a
short to ground.
Perform 42RLE TRANSMISSION VERIFICATION TEST -
VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AU-
TOMATIC - 42RLE - STANDARD PROCEDURE)
No
>> Go To 7
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