Jeep Liberty KJ. Manual - part 1166

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When Monitored:
Continuously with the ignition on, engine running, with the transmission in gear.

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Set Condition:
The TCM continuously monitors Actual Line Pressure and compares it to Desired Line Pressure. If the Actual
Line Pressure reading is more than 172.4 kPa (25 psi) higher than the Desired Line Pressure, but is less than
the highest Line Pressure ever used in the current gear, the DTC sets.

Possible Causes

RELATED DTC’S PRESENT

LINE PRESSURE CONNECTOR AND WIRING

INTERNAL TRANSMISSION

TRANSMISSION CONTROL MODULE

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to
21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Theory of Operation

Line pressure is electronically controlled by the Transmission Control System and is measured by the Line Pressure
Sensor (LPS). The desired line pressure is continuously being compared to the actual line pressure and is regulated
by electronically changing the duty cycle of the Pressure Control Solenoid (PCS). (5% duty cycle = solenoid off =
max line pressure, 62% duty cycle = solenoid on = min line pressure).

The Transmission Control System calculates the desired line pressure based on inputs from the transmission and
engine. A calculated torque input to the transmission is used as the primary input of the desired line pressure cal-
culation and is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 to 931
kPa (120 to 135 PSI) during shifts and in Park and Neutral to ensure consistent shift quality.

Diagnostic Test

CHECK FOR RELATED DTCS

With the scan tool, check for other transmission DTCs.

Are there any other line pressure related DTC’s present?

Yes

>> Refer to the Transmission category and perform the appropriate symptom. Perform the test for P0934

and/or P0935 first if present. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/
545RFE - DIAGNOSIS AND TESTING)

>> Go To 2

CONDITION P0932 PRESENT

CAUTION: Apply Parking Brake
Start the engine.

CAUTION: Firmly apply the brakes.
With the scan tool, monitor the Line Pressure, Desired Line Pressure and the TPS degrees.

While firmly applying the brakes, place the shifter in reverse, then slowly press the accelerator pedal to a TPS
degree of 15°.

Compare the Line Pressure reading to the Desired Line Pressure reading on the scan tool.

Does the Line Pressure stay within ± 34 kPa or 5 PSI of the Desired Line Pressure?

>> Go To 3

Yes

>> Go To 5

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AUTOMATIC TRANSMISSION 545RFE - ELECTRICAL DIAGNOSTICS - (DIESEL)

CHECK LINE PRESSURE CONNECTOR AND WIRING

Ignition on, engine not running.

With the scan tool, monitor the Line Pressure Sensor voltage while wiggling the wiring harness and connectors
pertaining to the Line Pressure Sensor and the Transmission Solenoid/TRS Assembly.

Did the voltage remain steady while wiggling the wiring harness and connectors?

Yes

>> Go To 4

>> Disconnect and properly reconnect the Line Pressure Sensor connector. Inspect terminals and repair as

necessary.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

CHECK TCM 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.

With the Transmission Simulator select the

OFF

position on the

Input/Output Speed

switch.

Ignition on, engine not running.

With the scan tool, monitor the Line Pressure during the following step.

With the Transmission Simulator, turn the selector switch to each of the 3 Line Pressure positions.

NOTE: All three scan tool Line Pressure readings should be steady and ±14 kPa or 2.0 PSI of the reading
specified on the Transmission Simulator.

Does the Line Pressure on the scan tool fluctuate up and down more than 69 kPa or 10 PSI at any of
the 3 line pressure positions on the Transmission Simulator?

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 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

>> Repair internal transmission and inspect the oil pump per the Service information and replace if neces-

sary. If no problems are found, replace the Transmission Solenoid/TRS Assembly — possible cause is
the Pressure Control Solenoid is stuck.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

CHECK WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.

Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.

Wiggle the wires while checking for shorted and open circuits.

With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.

Where there any problems found?

Yes

>> Repair as necessary.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

>> Test Complete.

AUTOMATIC TRANSMISSION 545RFE - ELECTRICAL DIAGNOSTICS - (DIESEL)

21 - 609

P0934-LINE PRESSURE SENSOR CIRCUIT LOW

For a complete wiring diagram Refer to Section 8W.

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AUTOMATIC TRANSMISSION 545RFE - ELECTRICAL DIAGNOSTICS - (DIESEL)

•

When Monitored:
Continuously with the ignition on and engine running.

•

Set Condition:
This DTC will set when the monitored Line Pressure Sensor voltage is less than or equal to 0.35 volts for 0.18
seconds.

Possible Causes

(T39) 5-VOLT SUPPLY CIRCUIT OPEN

(T39) 5-VOLT SUPPLY CIRCUIT SHORT TO GROUND

(T38) LINE PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO GROUND

LINE PRESSURE SENSOR

TRANSMISSION CONTROL MODULE

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to
21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Theory of Operation

The monitored Line Pressure Sensor voltage should always be between 0.35 and 4.75 volts. Any monitored volt-
ages outside these parameters indicate an Line Pressure Sensor or wiring problem and will cause either DTC
P0934 or P0935 to set.

Diagnostic Test

CHECK IF DTC IS CURRENT

With the scan tool, check the STARTS SINCE SET counter for P0934.

NOTE: This counter only applies to the last DTC set.

Is the STARTS SINCE SET counter 2 or less?

Yes

>> Go To 2

>> Go To 6

CHECK TCM 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.

Ignition on, engine not running.

With the scan tool, under Transmission Sensors, monitor the Line Pressure.

Using the Transmission Simulator, set the rotary switch to each of the 3 line pressure positions.

AUTOMATIC TRANSMISSION 545RFE - ELECTRICAL DIAGNOSTICS - (DIESEL)

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