P0777
DTC P0776 or P0777
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 Descriptors
DTC P0776
- Pressure Control Solenoid Valve 2 Stuck Off
DTC P0777
- Pressure Control Solenoid Valve 2 Stuck On
Circuit/System Description
The clutch pressure control (PC) solenoid 2 is part of the control solenoid valve assembly which has no serviceable components. PC solenoid 2 regulates transmission fluid pressure to the 3-5-R regulator valve which controls pressure to the 3-5-R clutch. The transmission control module (TCM) calculates gear ratio based on the RPM signals from the 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
* 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.
* The engine speed is greater than 400 RPM for 5 seconds.
* The ignition voltage is 9.0 volts or greater.
* The transmission fluid temperature (TFT) is -7°C (19°F) or greater.
* The transmission output speed is 650 RPM or greater or the throttle position is 0.5 percent or greater.
* The throttle position signal is valid.
* The high side driver (HSD) is enabled.
P0777
* 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.
* The engine speed is greater than 400 RPM for 5 seconds.
* The ignition voltage is 9.0 volts or greater.
* The TFT is -7°C (19°F) or greater.
* The transmission output shaft speed is 200 RPM or greater.
* The throttle position signal is valid.
* 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 3 seconds and the transmission input shaft speed is 400 RPM or greater from the anticipated input shaft speed. This must occur 3 times.
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 second and the transmission input shaft speed is 400 RPM or less from the anticipated input shaft speed. This must occur 3 times.
Action Taken When the DTC Sets
P0776
* DTC P0776 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM limits the transmission to reverse and 2nd gear.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits TAP Up/TAP Down function.
* The TCM inhibits manual shifting of forward gears.
P0777
* DTC P0777 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM limits the transmission to reverse and 3rd gear.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits TAP Up/TAP Down function.
* The TCM inhibits manual shifting of forward gears.
Conditions for Clearing the DIC/DTC
DTCs P0776 and P0777 are Type A DTCs.
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 (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Circuit/System Verification
Warning
Apply the parking brake and block the drive wheels before performing this procedure in order to prevent bodily injury.
Note: If other DTCs are set, diagnose those DTCs first.
1. Engine idling in Park, with parking brake applied and drive wheels chocked.
2. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) , to verify correct fluid level and condition.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning) , to dislodge debris and free up the valves.
4. Monitor the Transmission Fluid Pressure Switch 1 parameter with a scan tool. Place the gear select lever in Park, Reverse, and Neutral range. Verify the Transmission Fluid Pressure Switch 1 parameter states are correct for Park, Reverse, and Neutral. Refer to Transmission Fluid Pressure Switch Logic (Transmission Fluid Pressure Switch Logic).
5. Place the gear select lever in Drive range. Command the shift transmission with a scan tool through all forward ranges. Verify the Transmission Fluid Pressure Switch 1 parameter states are correct for all forward ranges. Refer to Transmission Fluid Pressure Switch Logic (Transmission Fluid Pressure Switch Logic).
6. Engine idling in Park, verify with a scan tool the Transmission ISS/OSS Supply Voltage test status parameter displays OK.
7. Engine idling in Park. Observe the Transmission ISS parameter on the scan tool, while varying the engine speed. The Transmission ISS parameter should vary with engine speed and not drop out.
8. Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission OSS parameter on the scan tool. The Transmission OSS parameter should vary with the vehicle speed and not drop out.
Note: Perform a scan tool snapshot during the road test.
9. Perform the Road Test (Initial Inspection and Diagnostic Overview). Verify the transmission operation performs as indicated in the road test instructions.
10. Review the scan tool snapshot data. Verify the following transmission data parameters display the correct values for each gear range.
* Transmission ISS
* Transmission OSS
* Pressure Control Solenoid Valve 2 Pressure Command
* Transmission Fluid Pressure Switch 1
11. 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
Note: You must perform the Circuit/System Verification first.
1. Perform the Line Pressure Check (Line Pressure Check). Verify the transmission line pressures are 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 ranges, refer to Fluid Pressure High or Low (Fluid Pressure High or Low).
2. Ignition OFF, remove the control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement (Service and Repair).
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).
• If the control solenoid valve assembly does not pass the performance test, replace the control solenoid valve assembly.
4. Inspect for the following conditions and repair or replace as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) 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 (Programming and Relearning) for control solenoid valve assembly replacement, setup, and programming.
* Perform the Transmission Adaptive Values Learn (Programming and Relearning) following all transmission related repairs.
* Perform the:
- Internal Components Removal (8. Internal Components Removal)
- 3-5-Reverse and 4-5-6 Clutch Housing Disassemble (6T40/45) (21. 3-5-Reverse and 4-5-6 Clutch Housing Disassemble (6T40/45))
- 3-5-Reverse and 4-5-6 Clutch Housing Assemble (6T40/45/50) (22. 3-5-Reverse and 4-5-6 Clutch Housing Assemble (6T40/45/50))
- 3-5-Reverse and 4-5-6 Clutch Housing, and Input, Reaction, and Output Carrier Installation (24. 3-5-Reverse and 4-5-6 Clutch Housing, and Input, Reaction, and Output Carrier Installation)