Automatic Transmission - 6T70/6T75
DTC P1751
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC P1751
- Shift Valve 1 Performance
Circuit/System Description
The shift valve 1 (clutch select valve 2) is part of the lower control valve body. The shift valve 1 (clutch select valve 2) controls fluid to the R1 and 4-5-6 clutches. During this diagnostic test, intrusive actions are taken by the transmission control module (TCM) to test the clutch select valve 2 to see if the valve is stuck. The TCM commands the shift solenoid (SS) 1 ON to put pressure on the valve towards the spring and at the same time, elevates line pressure slightly to assist the spring side pressure. If the spring is broken, the valve will slip back towards the spring indicating a mechanical failure and the DTC will set.
Conditions for Running the DTC
* No ISS DTCs P0716 or P0717.
* No OSS DTCs P0722 or P0723.
* No TCC Performance DTCs P0741 or P0742.
* No TCC Electrical DTCs P2762, P2763, or P2764.
* The engine speed is greater than 500 RPM for greater than 5 seconds.
* The ignition voltage is between 8.6 volts and 19.0 volts.
* The transmission fluid temperature (TFT) is 20-130°C (68-266°F).
* The calc. throttle position is 8 percent or greater.
* The engine torque is greater than 80 Nm (59 lb ft).
* The transmission input speed is greater than 1100 RPM.
* No upshift or downshift in process.
Conditions for Setting the DTC
The TCM detects attained gear slip is 100 RPM or greater 5 times during 5 samples.
Action Taken When the DTC Sets
* DTC P1751 is a Type B DTC.
* The TCM freezes transmission adaptive functions.
Conditions for Clearing the DTC
DTC P1751 is a Type B DTC.
Reference Information
Description and Operation
Transmission General Description (Transmission General Description)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Perform the Transmission Fluid Check (Transmission Fluid Check) to verify correct fluid level and condition. The transmission fluid level should be within the crosshatch band and the transmission fluid should be red or dark brown.
• If the transmission fluid is low or discolored, refer to Transmission Fluid Replacement (Removal and Replacement).
2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning) to dislodge debris and free up the valves.
3. Operate the vehicle in drive with the calculated throttle position greater than 8 percent and ensure the TCC is commanded ON and OFF a minimum of 5 times. The DTCs should not set.
• If a DTC sets, inspect the lower control valve body for a stuck clutch select valve 2, a broken clutch select valve 2 spring, debris or damage and repair or replace as necessary.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Repair Instructions
Important: Perform the Service Fast Learn Adapts (Programming and Relearning) following all transmission related repairs.
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning)
* Control Valve Lower Body and Upper Body Replacement (Control Valve Lower Body and Upper Body Replacement)