Automatic Transmission - 6T70/6T75
DTC P0776 or P0777
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 Descriptors
DTC P0776
- Clutch Pressure Control (PC) Solenoid 2 - Stuck Off
DTC P0777
- Clutch Pressure Control (PC) Solenoid 2 - Stuck On
Circuit/System Description
The clutch pressure control (PC) solenoid 2 is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. The clutch PC solenoid 2 flows fluid to the 3-5-R clutch when commanded OFF and exhausts fluid when commanded ON. The clutch PC solenoid 2 regulates the transmission fluid pressure to the 3-5-R clutch. The TCM calculates gear ratio based on data from the automatic transmission input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.
Conditions for Running the DTC
P0776
* No ISS DTCs P0716 or P0717.
* No OSS DTCs P0722 or P0723.
* No IMS DTCs P1825 or P1915.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission input speed is 60 RPM or greater.
* 3-5-R clutch is commanded ON.
P0777
* No ISS DTCs P0716 or P0717.
* No OSS DTCs P0722 or P0723.
* No IMS DTCs P1825 or P1915.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission output shaft speed is 200 RPM or greater.
* 3-5-R clutch is commanded OFF.
Conditions for Setting the DTC
P0776
The TCM detects an incorrect on-coming clutch gear ratio, or flare, when the 3-5-R clutch is commanded ON for 2.25 seconds and the transmission input shaft speed is 100 RPM or greater from the anticipated input shaft speed.
P0777
The TCM detects an incorrect off-going clutch gear ratio, or tie-up, when the 3-5-R clutch is commanded OFF for 1.2 seconds and the transmission input shaft speed is 40 RPM or less from the anticipated input shaft speed.
Action Taken When the DTC Sets
* DTCs P0776 and P0777 are Type A DTCs.
* The TCM commands maximum line pressure.
* The TCM inhibits TCC.
* The TCM freezes transmission adaptive functions.
Conditions for Clearing the DIC/DTC
DTCs P0776 and P0777 are Type A DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Transmission General Description (Transmission General Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
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
* J 21867 Pressure Gage
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. Engine idling at operating temperature. Attempt to clean or free up a potential sticking valve with the scan tool Service Cleaning Procedure. Refer to Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning) for further instructions.
3. Operate the vehicle in drive with the calculated throttle position greater than 8 percent and ensure TCC is commanded ON and OFF a minimum of 5 times. The DTCs should not set.
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. Ignition OFF, remove the line pressure test hole plug and install the J 21867 to the transmission.
2. Perform the Line Pressure Check (Line Pressure Check). Verify the transmission line pressure gage 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.
3. Ignition OFF, remove the control solenoid (w/body and TCM) valve assembly.
4. Install the DT-47825 to the control solenoid (w/body and TCM) valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test) for detailed instructions.
5. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test). A pressure change should occur.
• If a pressure change does not occur, replace the control solenoid (w/body and TCM) valve assembly.
6. Inspect for the following conditions and repair/replace as necessary:
* The control valve lower body assembly for sticking valves, damage, scored bores, or debris
* The 3-5-R clutch assembly for damage
Repair Instructions
Important:
* Perform the Service Fast Learn Adapts (Programming and Relearning) 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 Valve Lower Body and Upper Body Replacement (Control Valve Lower Body and Upper Body Replacement)
* Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal (Overhaul)
* Control Module References (Programming and Relearning) for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming