Jeep Grand Cherokee WK. Manual — part 1418
P0643-SENSOR REFERENCE VOLTAGE 1 CIRCUIT HIGH (CONTINUED)
3.
CHECK (T72) SENSOR SUPPLY CIRCUIT VOLTAGE
While back probing, measure the voltage of the (T72) Solenoid Supply
Voltage circuit in the TCM harness connector.
Does the measured voltage match the voltage reading on the
scan tool ± 0.2 volts?
Yes
>> Go To 4
No
>> 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
CONTROL
MODULES/TRANSMISSION
CONTROL MODULE for the appropriate service proce-
dures.
Perform NAG1 TRANSMISSION VERIFICATION TEST -
VER 1.
4.
(T72) SENSOR SUPPLY VOLTAGE CIRCUIT SHORT TO ANOTHER CIRCUIT
Turn the ignition off to the lock position.
Disconnect the Transmission Electrohydraulic Control Unit Assembly
harness connector.
Disconnect all TCM harness connectors.
Measure the resistance between the (T72) Solenoid Supply Voltage
circuit and all other circuits in the Transmission Electrohydraulic Con-
trol Unit harness connector.
Is the resistance below 5.0 ohms between the (T72) Solenoid
Supply Voltage circuit and all other circuits in the Transmission
Electrohydraulic Control Unit Assembly harness connector?
Yes
>> Repair the (T72) Solenoid Supply Voltage circuit for a
short to another circuit(s).
Perform NAG1 TRANSMISSION VERIFICATION TEST -
VER 1.
No
>> 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
CONTROL
MODULES/TRANSMISSION
CONTROL MODULE for the appropriate service proce-
dures.
Perform NAG1 TRANSMISSION VERIFICATION TEST -
VER 1.
21 - 482
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
WK
P0643-SENSOR REFERENCE VOLTAGE 1 CIRCUIT HIGH (CONTINUED)
5.
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 wires while checking for shorted and open circuits.
Were there any problems found?
Yes
>> Repair as necessary.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
>> Test Complete.
WK
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
21 - 483
P0657-SOLENOID SUPPLY VOLTAGE CIRCUIT
21 - 484
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
WK
P0657-SOLENOID SUPPLY VOLTAGE CIRCUIT (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 Solenoid Supply Voltage output of the Transmission Control Module (TCM) provides the voltage to the three
shift, two pressure and TCC solenoids. The output is active whenever the system is in normal operation. If a major
system fault is detected, this output is turned off to ensure that no solenoids are active.
•
When Monitored:
When the output is active and no undervoltage condition exists.
•
Set Condition:
When the monitored supply voltage and battery voltage differ by 3.6 volts.
Possible Causes
(T78) SOLENOID SUPPLY VOLTAGE CIRCUIT OPEN
(T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO GROUND
(T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO VOLTAGE
(T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO ANOTHER CIRCUIT
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.
(T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO VOLTAGE
With the scan tool, check for other transmission DTCs.
Is the DTC P1629-TCM INTERNAL - SOLENOID SUPPLY/WATCHDOG also present?
Yes
>> When both P0657-SOLENOID SUPPLY VOLTAGE CIRCUIT and P1629-TCM INTERNAL - SOLENOID
SUPPLY/WATCHDOG DTCs set at the same time indicates that the (T78) Solenoid Supply Voltage cir-
cuit is shorted to voltage. Repair the Solenoid Supply Voltage circuit for a short to voltage. If no short to
voltage is present, using the schematics as a guide, check the Transmission Control Module (TCM) ter-
minals 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 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE for the appropriate
service procedures.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
>> Go To 2
WK
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
21 - 485
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