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: Pressure Control (PC) Solenoid 2 - Stuck OFF

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

Circuit/System Description

The clutch pressure control (PC) solenoid 2 is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. PC solenoid 2 controls transmission fluid pressure to the hybrid direct, 2-3-4 clutch regulator valve. When PC solenoid 2 is commanded ON, the TCM compares the known transmission fluid pressure (TFP) switch 3 state with the actual TFP switch 3 state. Depending one the commanded mode or gear, the clutch PC solenoid 2 controls fluid pressure to the following components:

In the ON position, PC solenoid 2 controls transmission fluid to the following components:

    • EVT 1 mode, oil is supplied to drive motors 1 and 2 for cooling and the hybrid low, 1-2 clutch.
    • EVT 2 mode, oil is supplied to drive motors 1 and 2 for cooling and the hybrid direct, 2-3-4 clutch.
    • Gear 1, oil is supplied to the hybrid low, 1-2 clutch and the 1-3 clutch.

In the ON position, PC solenoid 2 controls the transmission fluid to the following components:

    • Gear 2, oil is supplied to the hybrid low, 1-2 clutch and the hybrid direct, 2-3-4 clutch.
    • Gear 3, oil is supplied to the hybrid direct, 2-3-4 clutch and the 1-3 clutch.
    • Gear 4, oil is supplied to the hybrid direct, 2-3-4 clutch and the 4th clutch.

Conditions for Running the DTC

P0776 or P0777

    • The engine run time is greater than 1 second.
    • Shift solenoid (SS) valve 1 is not in a transition state.
    • The transmission line pressure is greater than 370  kpa (54 psi) and not fluctuating by greater than 30 kpa (4 psi).
    • Propulsion is active.

P0776

The clutch PC solenoid 2 commanded pressure is greater than 1800 kpa (261 psi) for 4.5 seconds.

P0777

The clutch PC solenoid 2 commanded pressure is less than 5 kpa (1 psi) for 4.5 seconds.

Conditions for Setting the DTC

P0776 - Fail Case 1

The clutch PC solenoid 2 commanded pressure is 1800 kpa (261 psi) and the TFP switch 2 state is Low for 30 seconds.

P0776 - Fail Case 2

The clutch PC solenoid 2 commanded pressure is 1800 kpa (261 psi) and the TFP switch 2 state is Low for 0.5 seconds greater than 5 times during a key cycle.

P0777 - Fail Case 1

The clutch PC solenoid 2 commanded pressure is 5 kpa (1 psi) and the TFP switch 2 state is High for 36 seconds.

P0777 - Fail Case 2

The clutch PC solenoid 2 commanded pressure is 5 kpa (1 psi) and the TFP switch 2 state is High for 1.25 seconds greater than 5 times during a key cycle.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

P0776 and P0777 are Type B DTCs.

Diagnostic Aids

When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

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 Kit

Circuit/System Verification

  1. Verify that DTCs P0721, P0722, P0723, P0966, P0967, P0969, P0970, P0971, P0973, P0974, P0976, P0977, P2720, P2721, P2728, P2729, or P2730 are not set.
  2. If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  3. Perform the Transmission Fluid Check procedure.
  4. Operate the vehicle in drive to obtain 72 km/h (45 mph), stop the vehicle, turn the ignition Off for at least 30 seconds. Perform this 2 times.
  5. If the DTC resets, go to Circuit/System Testing.

Circuit/System Testing

  1. Perform the Line Pressure Check procedure.
  2. If the pressure is out of specification, correct this concern first.
  3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
  4. If a concern is found, repair or replace the control solenoid (w/body and TCM) valve assembly.
  5. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test .
  6. If the solenoid is found to be leaking or stuck closed, replace the control solenoid (w/body and TCM) valve assembly.
  7. Inspect the control valve lower body assembly for sticking valves, damage, scored bores, or debris.
  8. If a concern is found in the valve body, repair or replace the valve body as necessary.
  9. Inspect the hybrid direct, 2-3-4 clutch assembly for damage.
  10. If a concern is found in the hybrid direct, 2-3-4 clutch assembly, repair or replace as necessary.

Component Testing

PC Sol 2 Operation

Operating Conditions

Normal Operation

Stuck OFF

Stuck ON

Steady State Gears 3

3

Neutral

3

Steady State Gears 1, 2, 4

1, 2, 4

1, 2, 4

3

Garage Shift

Park/Neutral to Reverse/Drive

Neutral

1 Drive Gear

Downshift from gears 4 to 3

3

Neutral

3

Upshift from gears 3 to 4

4

4

3

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Solenoid Valve and Transmission Control Module Assembly Replacement .
    •  Hybrid Direct, 2-3-4 Clutch Housing Overhaul for hybrid direct, 2-3-4 clutch assembly replacement.
    •  Control Module References for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.