6L50/6L80/6L90 - Automatic Transmission
DTC P0751
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (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 P0751
- Shift Solenoid (SS) 1 Valve Performance -Stuck Off
Diagnostic Fault Information
The following fault table will help determine if a hydraulic circuit or an incorrect position or application of a component affects the transmission operation.
Circuit/System Description
The shift solenoid (SS) valve 1 is part of the lower control valve body. The SS valve 1 is a normally closed (NC) solenoid valve and controls fluid to the clutch select valve 3- and related clutches. During this diagnostic test, intrusive actions are taken by the transmission control module (TCM) to test the SS valve 1 to see if the valve is stuck OFF. When in first gear engine braking, if first gear ratio is not achieved in a predetermined period of time and the closest gear ratio detected if fourth, the TCM commands second gear and if second gear ratio is attained this indicates a stuck OFF SS valve 1 and the DTC will set.
Conditions for Running the DTC
* First gear locked is commanded.
* Commanded gear slip is equal to or less than 75 RPM for 0.125 seconds.
Conditions for Setting the DTC
The TCM detects second gear ratio is achieved.
Action Taken When the DTC Sets
Depending when the vehicle was manufactured, DTC P0751 is either a Type A or Type B DTC.
Conditions for Clearing the DTC
Depending when the vehicle was manufactured, DTC P0751 is either a Type A or Type B DTC.
Diagnostic Aids
* When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions. Ensure the transmission fluid level is correct and there are no leaks.
* Under certain conditions where P0751 sets, the TCM provides functional status to other control modules. This may result in the module disabling the cruise control. For this condition, correct the DTC and then power-down to reset the TCM.
Reference Information
Schematic Reference
Drive Range, First Gear Engine Braking (Drive Range, First Gear Engine Braking)
Description and Operation
Transmission Component and System Description (Transmission Component and System 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
Special Tools
DT-47825 Control Solenoid Test Plate
Circuit/System Verification
1. Perform the Transmission Fluid Check (Transmission Fluid Check).
2. Operate the vehicle in drive from a complete stop, with the calculated throttle position greater than 15 percent to obtain 56 km/h (35 mph) 2 times.
• If the DTC resets, go to Circuit/System Testing.
Circuit/System Testing
1. Perform the Line Pressure Check (Line Pressure Check).
• If the pressure is out of specification correct that concern first.
2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning) and retest the DTC as outlined in the Circuit/System Verification steps.
• If the DTC resets, continue on with testing.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
• If a concern is found, repair or replace the control solenoid (w/body and TCM) valve assembly.
4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test).
• If the shift solenoid 1 is found to be leaking or stuck OFF, replace the control solenoid (w/body and TCM) valve assembly.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Replace the control solenoid (w/body and TCM) valve assembly. Refer to Control Module References (Programming and Relearning) for replacement, setup, or programming.
* Perform the Service Fast Learn Adapts (Programming and Relearning).