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 Valve 1 Performance - Stuck Off
DTC P0752
- Shift Solenoid Valve 1 Performance - Stuck On
Circuit/System Description
The shift solenoid (SS) valve 1 is part of the control solenoid valve assembly, which has no serviceable components. The solenoid operates by the transmission control module (TCM) opening or closing the ground circuit. With the solenoid circuit open, the plunger forces the metering ball against the actuator feed limit seat, blocking the flow and any existing pressure is exhausted through the exhaust port. With the solenoid circuit grounded, solenoid on, the internal plunger moves, allowing the metering valve to move away from the actuator feed limit seat and against the exhaust seat, creating signal fluid pressure. The signal fluid pressure acts against the clutch select valve 2 to overcome the valve spring force, moving the valve to the apply position. Fluid pressure from the R1/4-5-6 regulator valve flows through clutch select valve 2 and is directed to either the low and reverse clutch or the 4-5-6 clutch, depending on the position of clutch select valve 2.
Conditions for Running the DTC
P0751
* The ignition voltage is 8.6 volts or greater.
* 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 high side driver is enabled.
* The output shaft speed is greater than 0 RPM or the throttle position is greater than 0.5 percent.
* The transmission fluid temperature (TFT) is -7°C (19°F) or greater.
* DTC 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 is not set.
P0752
* The ignition voltage is 8.6 volts or greater.
* 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 0.5 percent.
* The TFT is -7°C (19°F) or greater.
* DTC 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 is not set.
Conditions for Setting the DTC
P0751
Commanded gear equals first lock, the gear ratio is 1.34-1.48, and gear box slip is 400 RPM or greater 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, 3rd gear is commanded, and gear box slip is 400 RPM or greater for 2.0 seconds, 5 times.
Action Taken When the DTC Sets
P0751
* DTC P0751 is a Type B DTC.
* The TCM inhibits 1st gear.
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, 1st, and 3rd gear 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 Control Module References 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 6T70/6T75 - Automatic Transmission 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 Valve 1
* Transmission Fluid Pressure Switch 1
* Transmission Fluid Pressure Switch 3
* Transmission Fluid Pressure Switch 4
* Transmission Fluid Pressure Switch 5
4. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
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 Q8 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 Q8 control solenoid valve assembly. A pressure change should occur for each solenoid.
• If the Q8 control solenoid valve assembly does not pass the performance test, replace the Q8 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
Note:
* Perform the Reset Transmission Adapts 6T70/6T75 - Automatic Transmission 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 Control Module References for control solenoid valve assembly replacement, setup, or programming