6T40/6T45 - Automatic Transmission
DTC P0776 or P0777
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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
Diagnostic Fault Information
The following fault table gives examples of how hydraulic circuit problems and malfunctioning hard parts affect the transmission operation.
Circuit/System Description
The clutch pressure control (PC) solenoid 2 is part of the control solenoid (w/body and TCM) valve assembly. The control solenoid (w/body and TCM) valve assembly has no serviceable parts. The PC solenoid 2 is a normally high-pressure control solenoid which provides fluid pressure to the 3-5-R clutch regulator valve which regulates the transmission fluid pressure to the 3-5-R clutch. The TCM controls the solenoid pressure by regulating the exhaust fluid. When the TCM commands the solenoid off, the exhausting fluid is stopped and the 3-5-R pressure is high. When commanded on, the clutch PC solenoid 2 regulates the amount of exhausting transmission fluid. Solenoid power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuits and components that the TCM powers. Should the circuit overload the driver will shutdown. After the overload is removed the HSD resets. 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 known transmission gear ratio to a 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 ignition voltage is between 9.0 volts and 19.0 volts.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission input speed is 60 RPM or greater.
* The 3-5-R clutch is commanded ON.
* The HSD is enabled.
P0777
* No ISS DTCs P0716 or P0717.
* No OSS DTCs P0722 or P0723.
* No IMS DTCs P1825 or P1915.
* The ignition voltage is between 9.0 volts and 19.0 volts.
* 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.
* The HSD is enabled.
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 4.0 seconds and the transmission input shaft speed is 33 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.
* The TCM inhibits TAP Up/TAP Down.
Conditions for Clearing the DIC/DTC
DTCs P0776 and P0777 are Type A DTCs.
Diagnostic Aids
* DTC P0776 detects neutral when 3rd or 5th gear is commanded.
* DTC P0777 detects a tie-up condition when shifting from 3rd or 5th.
* When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions.
* If diagnosing DTC P0776 and you know the 3-5-R Clutch is not stuck On, inspect for a sticking clutch select valve 2.
* If by shifting to reverse you obtain a neutral state, PC Sol. 2 could be stuck off. Perform a Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test) to verify the solenoid is stuck off.
* If by shifting to neutral you obtain a reverse state, PC Sol. 2 could be stuck on. Perform a Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test) to verify the solenoid is stuck on.
* Use the scan tool to view the TFP Switch status and refer to the Transmission Fluid Pressure Switch Logic table to determine when a TFP switch should be active or inactive for a given gear. This will help to determine if the hydraulic circuit functioning and if the PC solenoid or the valve train is in an incorrect position.
Reference Information
Schematic Reference
* Drive Range, Third Gear (Drive Range, Third Gear)
* Drive Range, Fifth Gear (Drive Range, Fifth Gear)
Description and Operation
* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
* DT-48616 Control Solenoid Test Plate
* DT-48616-10 Adapter Harness
Circuit/System Verification
1. Perform the Transmission Fluid Check (Transmission Fluid Check) .
2. Operate the vehicle in drive with the calculated throttle position greater than 15 percent to obtain 72 km/h (45 mph).
• If the DTC resets, go to Circuit/System Testing.
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Perform the Line Pressure Check (Line Pressure Check) .
• If the pressure is out of specification, correct this 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 solenoid is found to be leaking or stuck closed, replace the control solenoid (w/body and TCM) valve assembly.
5. Inspect the control valve lower body assembly for sticking valves, damage, scored bores, or debris.
• If a concern if found in the valve body, repair or replace the valve body as necessary.
6. Inspect the 3-5-R clutch assembly for damage.
• If a concern is found in the 3-5-R clutch assembly, repair or replace as necessary.
Component Testing
Operating the transmission under the following conditions will verify that the PC solenoid or a portion of the hydraulic control circuit is not functioning as it should.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Important: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection) .
* Refer to Control Module References for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.
* Perform the Service Fast Learn Adapts (Programming and Relearning) following all transmission related repairs.
* Perform the:
- Internal Components Removal (Overhaul)
- 3-5-Reverse and 4-5-6 Clutch Housing Disassemble (Overhaul)
- 3-5-Reverse and 4-5-6 Clutch Housing Assemble (Overhaul)
- 3-5-Reverse and 4-5-6 Clutch Housing, and Input, Reaction, and Output Carrier Installation (Overhaul)