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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: 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 : Gen 1
    •  Drive Range, Fifth Gear : Gen 1

Description and Operation

    •  Transmission General 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

Circuit/System Verification

    Warning: Apply the handbrake and chock 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 ticking over in Park, with handbrake applied and drive wheels chocked.
  2. Perform the Transmission Fluid Level and Condition Check , to verify correct fluid level and condition.
  3. 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 .
  4. 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 .
  5. Engine ticking over in Park, verify with a scan tool the Transmission ISS/OSS Supply Voltage test status parameter displays OK.
  6. Engine ticking over 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.

    8. Note: Perform a scan tool snapshot during the road test.

  8. Perform the Road Test . 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.
    10. • Transmission ISS
    • Transmission OSS
    • Pressure Control Solenoid Valve 2 Pressure Command
    • Transmission Fluid Pressure Switch 1
  10. 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 .

Circuit/System Testing

    Note: You must perform the Circuit/System Verification first.

  1. Perform the 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 : Gen 1 .
    2. ⇒If not within the specified ranges, refer to Fluid Pressure High or Low .
  2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement .
  3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test .
    4. ⇒If the Q8 control solenoid valve assembly does not pass the performance test, replace the Q8 control solenoid valve assembly.
  4. Inspect for the following conditions and repair or replace as necessary.

DTCs

Component

Condition

P0776

P0777

Control Valve Body Assembly

3-5-R Regulator Valve stuck/sticking - debris, binding, damaged valve, or scored bore

P0776

P0777

Q8 Control Solenoid Valve Assembly
    • Clutch Pressure Control Solenoid 2
    • O-ring seals leaking
    • Valve body filter plate assembly cracked, blocked, or damaged gasket seal

P0776

P0777

Control Valve Body Assembly
    • Actuator feed limit circuit supply fluid to solenoids restricted or not available - debris or sediment blockage
    • 3-5-R clutch regulator valve not in the applied position - debris, binding, damaged valve, or scored bore
    • Control valve body ball check valve not seating correctly - debris

P0776

P0777

Torque Converter (w/Fluid Pump) Housing Assembly

Fluid pump housing/gear damaged/scored

P0776

3-5-R and 4-5-6 Clutch Housing Assembly

3-5-R clutch backing plate retaining ring not seated, causing clutch pack over-travel

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

       Note: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

    • Refer to Control Module References for control solenoid valve assembly replacement, set-up, and programming.
    • Perform the Transmission Adaptive Values Learn following all transmission related repairs.
    • Perform the:
       -  Internal Components Removal
       -  3-5-Reverse and 4-5-6 Clutch Housing Disassemble : 6T40/45/50 - Gen 1
       -  3-5-Reverse and 4-5-6 Clutch Housing Assemble : 6T40/45/50 - Gen 1
       -  3-5-Reverse and 4-5-6 Clutch Housing, and Input, Reaction, and Output Carrier Installation
   


© Copyright Chevrolet. All rights reserved
   


© Copyright Chevrolet. All rights reserved