2007 Liberty KJ Factory Service Manual 21 - TRANSMISSION AND TRANSFER CASE

P0765-UD SOLENOID CIRCUIT





For a complete wiring diagram Refer to Section 8W

Theory of Operation


The Transmission Control System uses six electronically controlled solenoids that allow hydraulic fluid to be applied to various friction elements (clutches), which enables the gear requested. The continuity of each solenoid circuit is periodically tested. Each inactive solenoid is turned on for a few milliseconds, then off. Each active solenoid is turned off for a few milliseconds, then on. This pulsing of voltage to the solenoid causes an inductive spike which can be sensed by the Transmission Control System. If an inductive spike is not sensed by the Transmission Control System during the continuity check, it is tested again. If the test fails three consecutive times, the appropriate Diagnostic Trouble Code (DTC) is set. If the solenoid test is run in response to a gear ratio or pressure switch error, one failure will result in setting the appropriate DTC. Note: This DTC is strictly an electrical fault and does not apply to any internal transmission failures.



Possible Causes
 
RELATED TCM POWER INPUT DTCS PRESENT
 
(T59) UD SOLENOID CONTROL CIRCUIT SHORT TO OTHER CIRCUITS
 
(T59) UD SOLENOID CONTROL CIRCUIT OPEN
 
(T59) UD SOLENOID CONTROL CIRCUIT SHORT TO GROUND
 
TRANSMISSION SOLENOID/TRS ASSEMBLY
 
TRANSMISSION CONTROL MODULE
 


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



Diagnostic Test

1. DETERMINE IF RELATED TCM POWER INPUT DTCS ARE PRESENT

With the scan tool, read Transmission DTCs

Are there any TCM Power Input DTCs present also?

Yes


No

2. CHECK IF DTC P0765 IS PRESENT

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 Transmission Simulator, Miller tool #8333.
Ignition on, engine not running.
With the scan tool, actuate the UD Solenoid.
Monitor the UD Solenoid LED on the Transmission Simulator.

Did the UD Solenoid LED on the Transmission Simulator blink on and off?

Yes


No

3. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY

With the Transmission simulator still connected, continue to actuate the UD solenoid for 2 minutes.
After 2 minutes of actuation, with the scan tool, stop the actuation and check for transmission DTCs.

Did the DTC P0765 reset during the actuation test?

Yes


No

4. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY

With the Transmission simulator still connected, continue to actuate the UD solenoid for another 2 minutes while wiggling the related wiring harness and connectors.
With the scan tool, stop the actuation and check for transmission DTCs.

Did the DTC P0765 reset during the actuation test?

Yes


No

5. CHECK THE (T59) UD SOLENOID CONTROL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT



Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333.
Disconnect the TCM harness connector.
Measure the resistance between the (T59) UD Solenoid Control circuit and all other circuits in the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance below 5.0 ohms between the (T59) UD Solenoid Control circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes


No

6. CHECK THE (T59) UD SOLENOID CONTROL CIRCUIT FOR AN OPEN



Measure the resistance of the (T59) UD Solenoid Control circuit between the Transmission Solenoid/TRS Assembly harness connector and the TCM harness connector.

Is the resistance above 5.0 ohms?

Yes


No

7. CHECK THE (T59) UD SOLENOID CONTROL CIRCUIT FOR A SHORT TO GROUND



Measure the resistance between ground and the (T59) UD Solenoid Control circuit.

Is the resistance below 5.0 ohms?

Yes


No