Jeep Grand Cherokee WK. Manual — part 1443
P1644-INCORRECT VARIANT/CONFIGURATION
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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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P1644-INCORRECT VARIANT/CONFIGURATION (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. If the
TCM detects that the variables that dictate the vehicle application are not present, the controller will enter Limp-in
mode and illuminate the MIL.
•
When Monitored:
Continuously with the ignition on.
•
Set Condition:
If the TCM detects that the variables that dictate the vehicle application are not present.
Possible Causes
CONTROLLER NOT CODED
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 IF TCM IS FLASHABLE
NOTE: Controller is programmed with generic software and will not allow the correct vehicle Powertrain
management.
With the scan tool, record the vehicles controller part number.
Select Use Controller Part Number under the Flash Tab.
Flash the controller with the correct software.
Were you able to update (flash) the controller successfully?
Yes
>> Test Complete.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
>> Replace the TCM per the Service Information. Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
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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P1704-INPUT SPEED SENSOR 1 OVERSPEED
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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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P1704-INPUT SPEED SENSOR 1 OVERSPEED (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 NAG1 transmission has two input speed sensors 1 and 2 (N2 and N3), both speed sensors are located on the
valve body. The speed sensors are hall effect speed sensors that are used by the Transmission Control Module
(TCM) to calculate the transmissions input speed. Since the input speed could not be measured directly, two of the
drive elements are measured. Two input speed sensors were required because both drive elements are not active
in all gears.
The input speed sensors 1 and 2 will report the same input speed in gears 2nd, 3rd or 4th. If the 1 and 2 input
speed sensor signals are not the same in these gears, the TCM will set the DTC P2784-Input Speed Sensor 1/2
Correlation. The input speed sensor 2 is not reported in 1st and 5th gears. The input speed sensor 1 (N2) is not
reported in Reverse. The P01704-Input Speed Sensor 1 Overspeed and P01705-Input Speed Sensor 2 Overspeed
DTCs are rationality checks designed to detect a major transmission failure. If either DTC is detected, the TCM will
place the transmission in Neutral.
•
When Monitored:
Continuously with the ignition on, engine running, transmission in gear, and Input Speed Sensor 1 (N2) greater
than 0 RPM
•
Set Condition:
If the RPM of the Input Speed Sensor 1 (N2) is greater than 7700 RPM.
Possible Causes
INTERNAL TRANSMISSION
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 TO SEE IF DTC IS CURRENT
Turn the ignition on.
With the scan tool, erase Transmission DTCs.
Raise the vehicle on the hoist.
Start the engine.
With the scan tool, monitor the Input Speed Sensor 1 RPM.
Firmly apply the brakes and place the gear selector in Drive.
WARNING: To avoid personal injury or death, keep hands and feet clear of rotating wheels.
Release the brakes and raise the engine RPM to allow the transmission to upshift to the 2-3 and 3-4 shift schedule.
Did the Input Speed Sensors 1 display an RPM above 7700?
Yes
>> Go To 2
No
>> Go To 3
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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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