6T70/6T75 - Automatic Transmission
DTC P0751 or P0752
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P0751
- Shift Solenoid (SS) 1 Valve Performance - Stuck Off
DTC P0752
- Shift Solenoid (SS) 1 Valve Performance - Stuck On
Circuit/System Description
The shift solenoid (SS) valve 1 is part of the control solenoid valve assembly. The SS valve 1 is a normally closed (NC) solenoid valve and controls fluid to the clutch select valve 2. The solenoid operates by the transmission control module TCM opening or closing the ground circuit. With the solenoid circuit grounded, solenoid on, the internal plunger moves and allows the metering ball to move away from the feed seat and against the exhaust seat, creating signal fluid pressure. The signal fluid acts against the clutch select valve 2 to overcome the valve spring force, moving it to the apply position.
Conditions for Running the DTC
P0751
* The ignition voltage is greater than 8.6 volts.
* The engine speed is 400 RPM or greater for 5.0 seconds.
* The throttle position signal is valid.
* The engine torque signal is valid.
* The output shaft speed is greater than 0 RPM or the throttle position is greater than 0.4 percent.
* The transmission fluid temperature is 0°C (32°F) or greater.
* No DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E.
P0752
* The ignition voltage is greater than 8.6 volts.
* The engine speed is 400 RPM or greater for 5.0 seconds.
* The high side driver is enabled.
* The throttle position signal is valid.
* The output shaft speed is greater than 0 RPM, or the throttle position is greater than 0.4 percent.
* The transmission fluid temperature is 0°C (32°F) or greater.
Conditions for Setting the DTC
P0751
Commanded gear equals first lock, the gear ratio is 1.34-1.48, and gear box slip is greater than 200 RPM for 0.3 second, 8 times.
P0752
The transmission has achieved 1st Locked, 1st Free-Wheel, or 2nd, the 456/R1 pressure switch is pressurized, and gear box slip is greater than 200 RPM for 2 seconds, 5 times.
Action Taken When the DTC Sets
P0751
* DTC P0751 is a Type B DTC.
* The TCM inhibits first range.
P0752
* DTC P0752 is a Type A DTC.
* The TCM freezes transmission adaptive functions.
* The TCM commands maximum line pressure.
* The TCM inhibits Tap Up/Down function.
* The TCM inhibits manual shifting of forward gears.
* The TCM limits the transmission to reverse, first, and third range operation.
Conditions for Clearing the DTC
P0751
DTC P0751 is a Type B DTC.
P0752
DTC P0752 is a Type A DTC.
Diagnostic Aids
Before performing a road test, configure and setup the scan tool for snapshot mode. This allows you to display, monitor, and verify multiple transmission data parameters at one time, after the road test.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (6T70/6T75 - Automatic Transmission)
Connector End View Reference
* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)
Description and Operation
Transmission General Description (Transmission General Description)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Note: If other DTCs are set, diagnose those DTCs first.
1. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) to verify correct fluid level and condition.
Note: Perform a scan tool snapshot during the road test.
2. Perform the Road Test (6T70/6T75 - Automatic Transmission). Verify the transmission operation performs as indicated, in the road test instructions.
3. Review the scan tool snapshot transmission data parameters. Verify the engine and transmission data parameters display the correct values in all forward gear ranges:
* Engine Speed
* Transmission ISS
* Transmission OSS
* Vehicle Speed
* Shift Solenoid 1
* TFP Switch 1
* TFP Switch 3
* TFP Switch 4
* TFP Switch 5
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.
Circuit/System Testing
1. Perform the Line Pressure Check (Line Pressure Check). Verify the transmission line pressure gauge is within the range specified in the Line PC Solenoid Valve Pressure table. Refer to Solenoid Valve Pressure (Solenoid Valve Pressure).
• If not within the specified range, repair as necessary. Refer to Fluid Pressure High or Low (Fluid Pressure High or Low) for further diagnosis.
2. Ignition OFF, remove the control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement (6T70/6T75 - Automatic Transmission).
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test). Test all solenoids on the control solenoid valve assembly. A pressure change should occur for each solenoid.
• If the control solenoid valve assembly does not pass the performance test, replace the control solenoid valve assembly.
4. Listed in the table below are conditions for each component that could set DTC P0751 or P0752. Carefully inspect each component for that condition. Repair or replace as necessary.
Repair Instructions
Important:
* Perform the Service Fast Learn Adapts (Service Fast Learn Adapts) following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for control solenoid valve assembly replacement, setup, or programming