P0776
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
- 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 valve assembly, which has no serviceable components. The PC solenoid 2 regulates transmission fluid pressure to the 3-5-Reverse clutch regulator valve which controls pressure to the 3-5-Reverse 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
* No ISS 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.
* The ignition voltage is greater than 8.6 volts.
* The engine speed is greater than 400 RPM for 5 seconds.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission output speed is 16 RPM or greater, or the throttle position is 0.4 percent or greater.
* The throttle position signal is valid.
* The high side driver is commanded ON.
P0777
* 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.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission output shaft speed is 350 RPM or greater.
* The transmission input speed is 200 RPM or greater.
* The commanded gear is not 1st range.
* The high side driver 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 200 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
P0776
* DTC P0776 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM inhibits Tap Up/Down function.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits manual shifting of forward gears.
* The TCM limits the transmission to 2nd, 4th, or reverse operation.
P0777
* DTC P0777 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM inhibits Tap Up/Down function.
* The TCM inhibits manual shifting of forward gears.
* The TCM freezes transmission adaptive functions.
* The TCM limits the transmission to 3rd and reverse operation.
Conditions for Clearing the DIC/DTC
DTCs P0776 and P0777 are Type A DTCs.
Diagnostic Aids
Before performing a road test, configure and setup the scan tool for snapshot mode. This will allow 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 (Diagrams)
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)
Circuit/System Verification
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. Monitor the Transmission Fluid Pressure (TFP) Switch 1 with a scan tool. Place the gear select lever in Park, Reverse, and Neutral range. Verify the TFP Switch 1 parameter states are correct for Park, Reverse, and Neutral. Refer to Transmission Fluid Pressure Switch Logic (Transmission Fluid Pressure Switch Logic).
4. Place the gear select lever in Drive range. Command the shift transmission with a scan tool through all forward ranges. Verify the TFP Switch 1 parameter states are correct for all forward ranges. Refer to Transmission Fluid Pressure Switch Logic (Transmission Fluid Pressure Switch Logic).
5. Engine idling in Park, verify with a scan tool the Transmission ISS/OSS Supply Voltage parameter displays OK.
6. 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.
7. 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.
8. Perform the Road Test (Initial Inspection and Diagnostic Overview). Verify the transmission operation performs as indicated in the road test instructions.
9. Review the scan tool snapshot data. Verify the following transmission data parameters display the correct values for each gear range:
* Transmission ISS
* Transmission OSS
* PC Solenoid 2
* TFP Switch 1
10. 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 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 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). A pressure change should occur for each solenoid valve.
• 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 P0776 or P0777. Carefully inspect each component for that condition. Repair or replace as necessary.
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 (8. Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal)
* Control Module References (Programming and Relearning) for control solenoid valve assembly replacement, setup, and programming