Page 2897 of 5267

When Monitored:
Every 7msec after a controller reset with transmission in neutral.
Set Condition:
After a PCM reset in neutral and Input and Output sensor ratio equals 2.50 to1.0 ± 50.0 RPM.
Possible Causes
SPEED SENSOR GROUND CIRCUIT OPEN
POWERTRAIN CONTROL MODULE
Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
Theory of Operation
The input and output speed sensors use a common ground circuit. The loss of this common ground results in the
input signal being sensed for both. After a reset in neutral, and after observing a specific ratio, the Speed Check
Fault Counter will increment. Because the speed sensors and the thermistor share the same ground circuit, this
DTC may indicate a loss of the common speed sensor ground. In some cases thisfault will cause a Gear Ratio
Error DTC to be set.
Diagnostic Test
1.PCM AND WIRING
Turn the ignition off to the lock position.
Remove the Ignition Switch Feed fuse from the TIPM.
CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being
startedingear.
WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in
personal injury or death.
Install the Transmission Simulator,Miller tool #8333 and the ElectronicTransmission Adapter kit 8333-1A.
Ignition on, engine not running.
With the Transmission Simulator, set the
Input/Output Speedswitch toONand the rotary switch to the3000/
1250
position.
With the scan tool, monitor the Input and Output Speed Sensor readings.
Does the Input Speed read 3000 RPM and the Output Speed read 1250 RPM, ± 50 RPM?
Ye s>>
Go To 2
No>>
Go To 3
Page 2898 of 5267

2.(T13) SPEED SENSOR GROUND CIRCUIT OPEN
Turn the ignition off to the lock position.
Disconnect the PCM C4 harness connector.
Disconnect the Input and Output Speed Sensor harness connectors.
CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting
in poor terminal to pin connection. Install Miller tool #8815 to per-
form diagnosis.
Measure the resistance of both of the (T13) Speed Sensor Ground cir-
cuits from the appropriate terminal of special tool #8815 to the Input
and Output Speed Sensor harness connectors.
Is the resistance above 5.0 ohms on either circuit?
Ye s>>
Repair the (T13) Speed Sensor Ground circuit for an open.
Perform 42RLE TRANSMISSION VERIFICATION TEST -
VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AU-
TOMATIC - 42RLE - STANDARD PROCEDURE)
No>>
Using the schematics as a guide, check the Powertrain
Control Module (PCM) terminals for corrosion, damage, or
terminal push out. Pay particular attention to all power and
ground circuits. If no problems are found, replace the PCM
per the Service Information.With the scan tool, perform
QUICK LEARN
Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
3.INTERMITTENT WIRING AND CONNECTORS
The conditions necessary to set the DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specifictothiscircuit.
Wiggle the wires while checking for shorted and open circuits.
With the scan tool, check the DTC EVENT DATA to help identify the conditionsin which the DTC was set.
Were there any problems found?
Ye s>>
Repair as necessary.
Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
No>>
Te s t C o m p l e t e .
Page 2899 of 5267

P1797-MANUAL SHIFT OVERHEAT
For a complete wiring diagramRefer to Section 8W.
When Monitored:
Continuously with engine running.
Set Condition:
If the Engine Temperature exceeds 123° C (255° F) or the Transmission Temperature exceeds 135° C (275° F)
while in AutoStick
mode. Note: Aggressive driving or driving in low for extended periods of time will set this
DTC.
Possible Causes
MANUAL SHIFT OVERHEAT
Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
Theory of Operation
The major cause of heat build up in the transmission is torque converter slip.WiththetransmissionintheAuto-
Stick
mode, the torque converter can slip during aggressive driving or heavy loading conditions such as trailer
towing or driving up steep grades. In the non AutoStick
mode, internal controller logic prevents the transmission
from overheating by managing the shift and EMCC schedule. In the AutoStick
mode, when the transmission or
engine temperature approaches an overheat condition, the manual shift overheat DTC sets and the AutoStick
mode is temporarily suspended until the temperature returns to normal.
Diagnostic Test
1.MANUAL SHIFT OVERHEAT
This is an informational DTC only.
With the scan tool, check the DTC EVENT DATA to help identify the conditionsin which the DTC was set.
Check the engine and transmission cooling system for proper operation.
Check the Radiator Cooling Fan operation.
Check the Transmission Cooling operation.
Check the Transmission Fluid Level per the Service Information to verify that it is not overfilled.
NOTE: Aggressive driving or driving in low for extended periods of time will set this DTC.
If there are no possible causes remaining, view repair.
Repair
If the Transmission Fluid is low, repair any Transmission Fluid leak as necessary and adjust the Trans-
mission Fluid Level per the Service Information. Refer to Service Information for the related symptoms
and repair as necessary.
Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
Page 2900 of 5267
U0100 LOST COMMUNICATION WITH ECM/PCM
For a complete wiring diagramRefer to Section 8W.
Page 2901 of 5267
When Monitored:
Every 7 msec with:
1) Engine speed greater than 500 RPM.
2) Battery voltage between 10 and 16 volts.
Set Condition:
CAN C BUS messages are not received for 10 seconds.
Theory of Operation
The NGC controller communicates over the CAN C BUS. The transmission controller continuously monitors BUS
activity. The CAN C BUS is also used to communicate transmission MIL statusto the Engine Controller. If the
Engine Controller is unable to communicate with the Transmission Controller, a DTC will set and the Engine Con-
troller will illuminate the MIL.
Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING for diagnostic
procedures and for further possible causes.
Page 2902 of 5267
U0002 CAN C BUS OFF PERFORMANCE
For a complete wiring diagramRefer to Section 8W.
Page 2903 of 5267
When Monitored:
Every 7 msec with:
1) Engine speed greater than 500 RPM.
2) Battery voltage between 10 and 16 volts.
Set Condition:
CAN C BUS messages are not received for 10 seconds.
Theory of Operation
The NGC controller communicates over the CAN C BUS. The transmission controller continuously monitors BUS
activity. The CAN C BUS is also used to communicate transmission MIL statusto the Engine Controller. If the
Engine Controller is unable to communicate with the Transmission Controller, a DTC will set and the Engine Con-
troller will illuminate the MIL.
Diagnose the U0002 CAN C BUS OFF PERFORMANCE as the U0001 CAN C BUS CIRCUIT test in 8-ELEC-
TRICAL/ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING for diagnostic procedures and for
further possible causes.
Page 2904 of 5267
U0121 LOST COMMUNICATION WITH ABS
For a complete wiring diagramRefer to Section 8W.