6T30/6T40/6T45/6T50 - Automatic Transmission (Gen 1)
DTC P0776 or P0777 (Gen 1)
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.
* Engine speed is 400 RPM or greater for 5 seconds.
* Ignition voltage is 9.0 volts or greater.
* Transmission fluid temperature (TFT) is -7°C (19°F) or greater.
* Transmission output speed is 650 RPM or greater or the throttle position is 0.5 percent or greater.
* Throttle position signal is valid.
* 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.
* Engine speed is 400 RPM or greater for 5 seconds.
* Ignition voltage is 9.0 volts or greater.
* TFT is -7°C (19°F) or greater.
* Transmission output shaft speed is 200 RPM or greater.
* Throttle position signal is valid.
* 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 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.
* TCM commands maximum line pressure.
* TCM limits the transmission to reverse and 2nd gear.
* TCM freezes transmission adaptive functions.
* TCM inhibits TAP Up/TAP Down function.
* TCM inhibits manual shifting of forward gears.
P0777
* DTC P0777 is a Type A DTC.
* TCM commands maximum line pressure.
* TCM limits the transmission to reverse and 3rd gear.
* TCM freezes transmission adaptive functions.
* TCM inhibits TAP Up/TAP Down function.
* 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 (Gen 2/Hybrid)
* Drive Range, Fifth Gear (Gen 2/Hybrid)
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:
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. Verify correct transmission fluid level and condition. Refer to Transmission Fluid Level and Condition Check Transmission Fluid Level and Condition Check.
3. Verify with a scan tool the Transmission Fluid Pressure Switch 1 parameter values are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic.
• If not the correct values for TFP Switch 1
Refer to Circuit/System Testing below.
• If TFP Switch 1 values are correct
4. Gear select lever in Drive range. Verify the Transmission Fluid Pressure Switch 1 parameter states are correct for all forward ranges when commanded with a scan tool. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic.
• If not the correct values for TFP Switch 1
Refer to Circuit/System Testing below.
• If TFP Switch 1 values are correct
5. Ignition ON, clear the TCM DTCs.
6. Perform the Road Test Initial Inspection and Diagnostic Overview. Verify the transmission operation performs as indicated in the road test instructions and DTCs P0776 or P0777 did not set.
• If DTC P0776 or P0777 sets
Refer to Circuit/System Testing below.
• If DTC P0776 or P0777 did not set
7. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
Note:
You must perform the Circuit/System Verification first.
1. Verify the transmission line pressures are within the range specified in the Line PC Solenoid Valve Pressure table. Refer to Line Pressure Check Line Pressure Check and Solenoid Valve Pressure (Gen 1) Solenoid Valve Pressure (Gen 1)Solenoid Valve Pressure (Gen 2) Solenoid Valve Pressure (Gen 2).
• If the line pressures are not within the specified ranges
Refer to Fluid Pressure High or Low Fluid Pressure High or Low.
• If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 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. Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid tested.
• If a pressure change does not occur for each solenoid
Replace the Q8 control solenoid valve assembly.
• If a pressure change occurs for each solenoid
4. Listed in the chart 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
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
Note:
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, programming and setup.
* Perform the Transmission Adaptive Values Learn Programming and Relearning following all transmission related repairs.
* Perform the:
- Internal Components Removal 9. Internal Components Removal
- 3-5-Reverse and 4-5-6 Clutch Housing Disassemble (6T40/45/50 - Gen 2)
- 3-5-Reverse and 4-5-6 Clutch Housing Assemble (6T40/45/50 - Gen 2)
- 3-5-Reverse and 4-5-6 Clutch Housing, and Input, Reaction, and Output Carrier Installation