GM Service Manual Online
For 1990-2009 cars only

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:  Clutch Pressure Control (PC) Solenoid 2 - Stuck Off

DTC P0777:  Clutch Pressure Control (PC) Solenoid 2 - Stuck On

Diagnostic Fault Information

The following fault table will help determine if a hydraulic circuit or an incorrect position of a valve train component affects the transmission operation.

Component

Cause

DTCs

1-2-3-4 and 3-5-R Clutch Housing Assembly

1-2-3-4 clutch backing plate retaining ring not seated, causing the piston to over-travel and cut 1-2-3-4 clutch piston seal

P0776

P0777

4-5-6 Clutch Housing

4-5-6 Housing broken hub weld

P0776

Control Solenoid (w/body and TCM) Valve Assembly

    • Clutch pressure control solenoid 2:
       - Always exhausting (Stuck On)
       - Not exhausting (Stuck Off)
       - Needle piston or armature pin binding
       - Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal
       - O-ring seals leaking
    • Valve body filter plate assembly cracked, blocked or damaged gasket seal

P0776

P0777

Fluid Pump Cover Assembly

Fluid pump cover vanes and fluid pump rotor broken - wrong pump rotor installed

P0776

Fluid Pump Cover Assembly

Isolator valve sticking or stuck - debris, sediment, binding or scored bore

P0776

P0777

Upper Control Valve Body

3-5-R regulator valve stuck - debris, sediment, binding or scored bore

P0776

Upper Control Valve Body

    • Actuator feed limit circuit supply fluid to solenoid restricted or not available (debris or sediment blockage)
    • B-R-1 and 4-5-6 clutch regulator valve not in the applied position - debris, sediment, binding or scored
    • 4-5-6 clutch boost valve not exhausting - binding or scored bore

P0776

P0777

Upper Control Valve Body

The B-2-6 regulator valve stuck - debris, sediment, binding or scored bore

P0777


Transmission Gear Range to PC Solenoid Valve Operation

Gear

1-2-3-4 CL PC SOL 5

2-6 CL PC SOL 4

3-5 REV CL PC SOL 2

LOW REV 4-5-6 CL PC SOL 3

Park

OFF

OFF

OFF

ON

Reverse

OFF

OFF

ON

ON

Neutral

OFF

OFF

OFF

ON

1st Braking

ON

OFF

OFF

ON

1st

ON

OFF

OFF

OFF

2nd

ON

ON

OFF

OFF

3rd

ON

OFF

ON

OFF

4th

ON

OFF

OFF

ON

5th

OFF

OFF

ON

ON

6th

OFF

ON

OFF

ON

Circuit/System Description

The clutch pressure control (PC) solenoid 2 is integral to the control solenoid (w/body and TCM) valve assembly and has no serviceable parts. The PC solenoid 2 is a normally high-pressure control solenoid which provides fluid pressure to the 3-5-R clutch regulator valve. The TCM controls the solenoid pressure by regulating the exhaust fluid. When the TCM commands the solenoid off, the exhausting fluid is stopped and the 3-5-R pressure is high. When commanded on, the clutch PC solenoid 2 regulates the amount of exhausting transmission fluid. Solenoid power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuits and components that the TCM powers. Should the circuit overload the driver will shutdown. After the overload is removed the HSD reset.

Conditions for Running the DTC

P0776

    • No DTCs P0716 or P0717 are active or have failed this key on.
    • No DTCs P0722 or P0723 are active or have failed this key on.
    • No DTC P1825 is active or has failed this key on.
    • Ignition voltage is between 8.6-18.0 volts.
    • Transmission fluid temperature (TFT) is equal to or greater than 0°C (32°F).
    • TCM high side driver (HSD) 1 is enabled.
    • Average driven wheel speed is 80  RPM or more.
    • Side to side average wheel speed between driven and non-driven wheel is 150 RPM or less for 6 seconds.
    • The transmission input shaft speed is greater than 60 RPM.
    • PC solenoid 2 is commanded On.
    • 3rd (1.532:1) or 5th (0.852:1) gear ratio has been achieved.

P0777

    • No DTCs P0716 or P0717 are active or have failed this key on.
    • No DTCs P0722 or P0723 are active or have failed this key on.
    • No DTC P1825 is active or has failed this key on.
    • TFT is equal to or greater than 0°C (32°F).
    • The transmission input and output shaft speed is greater than 200 RPM.
    • PC solenoid 2 is commanded Off.

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 2.25 seconds and the transmission input shaft speed is greater than 60 to 100 RPM 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 greater than 40 RPM from the anticipated input shaft speed.

Action Taken When the DTC Sets

    • DTCs P0776 and P0777 are Type A DTCs.
    • The TCM commands maximum line pressure.
    • The TCM inhibits TCC.
    • The TCM freezes transmission adaptive functions.

Conditions for Clearing the DIC/DTC

DTCs P0776 and P0777 are Type A DTCs.

Diagnostic Aids

    • When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions.
    • If diagnosing a P0776 DTC and you know the 3-5-R Clutch is not stuck On, inspect for a sticking clutch select valve 2.
    • If by shifting to reverse you obtain a neutral state, PC Sol. 2 could be stuck off. Perform a Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test to verify the solenoid is stuck off.
    • If by shifting to neutral you obtain a reverse state, PC Sol. 2 could be stuck on. Perform a Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test to verify the solenoid is stuck on.
    • Use the scan tool to view the TFP Switch status and refer to the Transmission Fluid Pressure Switch Logic table to determine when a TFP switch should be active or inactive for a given gear. This will help to determine if the hydraulic circuit functioning and if the PC solenoid or the valve train is in an incorrect position.

Reference Information

Schematic Reference

    •  Drive Range, Third Gear
    •  Drive Range, Fifth Gear

Description and Operation

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

Special Tools

DT-47825 Control Solenoid Test Plate

Circuit/System Verification

  1. Perform the Transmission Fluid Check . The fluid must be full and in good condition.
  2. Start engine in park and wait a moment. Shift to Reverse, pause, and then shift to Drive (D6) without allowing the vehicle to move.
  3. View scan tool parameters Commanded Gear and Gear Ratio.
  4. Operate the vehicle in drive from a complete stop, with the calculated throttle position greater than 15 percent to obtain 56 km/h (35 mph) or more.
  5. Make certain 3rd, 5th and Reverse gears are attainable. Use the two scan tool parameters and refer to the Shift Solenoid Valve State and Gear Ratio table to verify the correct ratio for the commanded gear.
  6. If the DTC resets, go to Circuit/System Testing.

Circuit/System Testing

  1. Perform the Line Pressure Check .
  2. If the pressure is out of specification, correct this concern first.
  3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning and retest the DTC as outlined in the Circuit/System Verification steps.
  4. If the DTC resets, continue with testing.
  5. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
  6. If a concern is found, repair or replace the control solenoid (w/body and TCM) valve assembly.
  7. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test .
  8. If the solenoid is found to be leaking or stuck closed, replace the control solenoid (w/body and TCM) valve assembly.
  9. Inspect the control valve upper body assembly for sticking valves, damage, scored bores, or debris.
  10. If a concern if found in the valve body, repair or replace the valve body as necessary.
  11. Inspect the 3-5-R clutch assembly for damage.
  12. If a concern is found in the 3-5-R clutch assembly, repair or replace as necessary.

Component Testing

Operating the transmission in the following condition will verify the PC solenoid or a portion of the hydraulic control circuit is not functioning as it should.

P0776: Clutch Pressure Control (PC) Solenoid 2 - Stuck Off

Transmission Operating Conditions

Transmission Condition if PC Sol. 2 is Stuck Off

Steady State: Gears 3rd or 5th

Neutral

Garage Shift: Park/Neutral to Reverse/Drive

Neutral

Downshift: from gears 6th, 5th, 4th to 5th or 3rd

Neutral


P0777: Clutch Pressure Control (PC) Solenoid 2 - Stuck On

Transmission Operating Conditions

Transmission Condition if PC Sol. 2 is Stuck On

Steady State: Gears 1st, 2nd, 4th, or 6th

3rd or 5th

Garage Shift: Park/Neutral to Reverse/Drive

1st (Engine Braking)

Downshift: from gears 4th, 5th, 6th to 3rd or 5th

3rd or 5th

Upshift: from gears 3rd, 5th to 4th, 5th, or 6th

3rd or 5th

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Control valve body replacement. Refer to Control Valve Lower Body and Upper Body Replacement .
    • 3-5-R clutch assembly repair or replace. Refer to 1-2-3-4 and 3-5 Reverse Clutch Overhaul .
    • Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.
    • Perform the Service Fast Learn Adapts if internal transmission repairs are performed.