Jeep Grand Cherokee WK. Manual — part 1438
P0778-SHIFT PRESSURE SOLENOID CIRCUIT (CONTINUED)
6.
INTERMITTENT 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 wiring and connectors while checking for any possible open or shorted circuits.
Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.
Were there any problems found?
Yes
>> Repair as necessary.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
>> Test Complete.
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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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P1629-TCM INTERNAL - SOLENOID SUPPLY/ WATCHDOG
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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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P1629-TCM INTERNAL - SOLENOID SUPPLY/ WATCHDOG (CONTINUED)
For the Transmission circuit diagram (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - SCHE-
MATICS AND DIAGRAMS)
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The Transmission Control Module (TCM) performs various internal tests to verify proper controller operation. During
the power up of the controller, the TCM tests the ability of the TCM to shut down the Solenoid Supply Voltage
circuit. The controller monitors the A/D feedback on the Solenoid Supply driver output to ensure that battery voltage
is no longer present. Note: A short to voltage on the Solenoid Supply Voltage circuit or any one of the solenoids
may set this DTC.
•
When Monitored:
Continuously with the ignition on.
•
Set Condition:
If the TCM detects voltage on the Solenoid Supply Voltage circuit when the TCM request the circuit to be off.
Possible Causes
(T78) SOLENOID SUPPY VOLTAGE CIRCUIT SHORT TO VOLTAGE
TRANSMISSION CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1.
CHECK THE (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT
Turn the ignition off to the lock position.
Disconnect the TCM C1 and C2 harness connectors.
Disconnect the Transmission Electrohydraulic Control Unit Assembly
harness connector.
Measure the resistance between the (T78) Solenoid Supply Voltage
circuit and every other circuit in the Transmission Electrohydraulic
Control Unit Assembly harness connector.
Is the resistance below 5.0 ohms between the (T78) Solenoid
Supply Voltage circuit and any other circuit(s) in the Transmis-
sion Electrohydraulic Control Unit Assembly harness connec-
tor?
Yes
>> Repair the (T78) Solenoid Supply Voltage circuit for short
to another circuit.
Perform NAG1 TRANSMISSION VERIFICATION TEST -
VER 1.
No
>> Go To 2
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P1629-TCM INTERNAL - SOLENOID SUPPLY/ WATCHDOG (CONTINUED)
2.
TRANSMISSION CONTROL MODULE
View repair
Repair
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. Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/TRANSMISSION CONTROL MODULE for the appropriate service procedures.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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