6T30/6T40/6T45 - Automatic Transmission
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. PC solenoid 2 regulates transmission fluid pressure to the 3-5-R regulator valve which controls pressure to the 3-5-R clutch. The 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 DTCs P0121, P0122, P0123, P0716, P0717, P0722, P0723, or P182E.
* The engine speed is greater than 500 RPM for 5 seconds.
* The ignition voltage is between 9.0 volts and 18.0 volts.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission output speed is 650 RPM or greater or accelerator pedal position is 1 percent or greater.
* The throttle position signal is valid.
* The HSD is enabled.
P0777 - Steady State
* DTC P182E is not set.
* The engine speed is greater than 500 RPM for 5 seconds.
* The ignition voltage is between 9.0 volts and 18.0 volts.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission output shaft speed is 650 RPM or greater.
* Throttle position is 1 percent or greater.
* Throttle position signal is valid.
Dynamic
* DTC P182E is not set.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The transmission ISS is greater than 200 RPM.
* The transmission OSS is greater than 350 RPM.
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.
P0777
The TCM detects an incorrect off-going clutch gear ratio, or tie-up, when the 3-5-R clutch is commanded OFF.
Action Taken When the DTC Sets
P0776
* DTC P0776 is a type A DTC.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits TAP Up/TAP Down.
* The TCM inhibits manual up, manual down shifts with the shift selector
* The TCM disables neutral idle.
* The TCM restricts the transmission second and fourth gears and reverse.
P0777 - Steady State or Dynamic
* DTC P0777 is a type A DTC.
* The TCM commands maximum line pressure.
* The TCM inhibits auto grade braking.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits TAP Up/TAP Down.
* The TCM disables neutral idle.
* The TCM defaults the transmission to third range when a forward range is selected.
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 allows you to monitor, display, and verify multiple transmission data parameters at one time, after the road test.
Reference Information
Schematic Reference
* Drive Range, Third Gear (Third Gear)
* Drive Range, Fifth Gear (Fifth Gear)
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)
* 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
Special Tools
* DT-48616 Control Solenoid Test Plate
* DT-48616-10 Adapter Harness
* J 21867 Pressure Gauge
Circuit/System Verification
Warning: Refer to Parking Brake and Drive Wheels Warning (Parking Brake and Drive Wheels Warning).
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 (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).
5. 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).
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 Tech 2 snapshot during the road test.
9. Perform the Road Test (6T30/6T40/6T45 - Automatic Transmission). Verify the transmission operation performs as indicated in the road test instructions.
10. Review the Tech 2 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
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 Service Fast Learn Adapts (6T30/6T40/6T45 - Automatic Transmission) following all transmission related repairs.