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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 Sierra - 2WD 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0974, P0977, or P2763

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 Descriptor

DTC P0974 : 1-2 Shift Solenoid (SS) Control Circuit High Voltage

DTC P0977 : 2-3 Shift Solenoid (SS) Control Circuit High Voltage

DTC P2763 : Torque Converter Clutch (TCC) Pressure Control (PC) Solenoid Control Circuit High Voltage

Circuit/System Description

The 1-2 shift solenoid (SS) valve and the 2-3 SS valve control transmission fluid pressure acting on the shift valves to position the valves for the appropriate gear. The 1-2 SS and the 2-3 SS valves are located on the control valve body. The transmission control module (TCM) commands the solenoid ON or OFF by switching the ground path. When the 1-2 SS valve or the 2-3 SS valve is commanded ON, the TCM senses low voltage. When the 1-2 SS valve or the 2-3 SS valve is commanded OFF, the TCM senses high voltage. The torque converter clutch pulse width modulated (TCC PWM) solenoid valve is a solenoid used to control the application and release of the converter clutch. When the solenoid is commanded OFF, the TCM senses high voltage. When the solenoid is commanded ON, the TCM senses low voltage.

Conditions for Running the DTC
    • The engine speed is 500 RPM for 5 seconds.
    • The 1-2 SS is commanded ON.

Conditions for Setting the DTC

The TCM commands the solenoid ON and the voltage feedback remains high B+.

Action Taken When the DTC Sets

P0974

    • DTC P0974 is a Type B DTC.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.

P0977

    • DTC P0977 is a Type A DTC.
    • The TCM commands maximum line pressure.
    • The TCM inhibits 4th gear.
    • The TCM freezes transmission adaptive functions.

P2763

    • DTC P2763 is a Type B DTC.
    • The TCM commands maximum line pressure.
    • The TCM forces TCC OFF.
    • The TCM inhibits 4th gear if in hot mode.
    • The TCM freezes transmission adaptive functions.

Conditions for Clearing the DTC
    • DTC P0974 and P2763 are Type B DTCs.
    • DTC P0977 is a Type A DTC.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Information

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

Transmission Control Module Scan Tool Information

Special Tools

    • J 35616 GM-Approved Terminal Test Kit
    • J 44152 Jumper Harness (20 Pins)

Circuit/System Verification

Start and idle the engine. Using the scan tool output controls, command the affected solenoid ON and OFF. Observing the CKT Status parameter on the scan tool for the affected solenoid, ensure that the parameter shows OK.

Circuit/System Testing
  1. Disconnect the AT inline 20-way connector. Install the J 44152 jumper harness (20 Pins), on the engine side of the AT inline 20-way connector. Using the J 35616 GM-approved terminal test kit, connect a test lamp between the affected control circuit and ground. Turn ON the ignition with the engine OFF. The test lamp should be OFF.
    2. ⇒If the test lamp is ON, test the affected control circuit for a short to voltage between the Fuse Block-Underhood and the AT inline 20-way connector.
  2. Disconnect the J 44152 from the engine harness. Connect the J 44152 to the transmission side of the AT inline 20-way connector. Using the J 35616 , measure the resistance between the affected control circuit and the ignition 1 voltage circuit. Resistance should be between 19-31 ohms for the 1-2 SS and the 2-3 SS. Resistance should be between 10-15 ohms for the TCC PWM solenoid valve.
    3. ⇒If the resistance is less than the specified value, test for a short to the ignition 1 voltage circuit or a faulty solenoid.
  3. Using the J 35616 , measure the resistance between the affected control circuit and all other circuits in the J 44152 except the ignition 1 voltage circuit and the other control circuits. Resistance should be greater than 250K ohms.
    4. ⇒If resistance is less than 250K ohms, test the control circuit for a short to another circuit.

Component Testing
  1. Using the J 44152 and the J 35616 measure the resistance between the ignition 1 voltage circuit and the affected control circuit. The resistance should be between 19-31 ohms for the 1-2 SS and the 2-3 SS. The resistance should be between 10-15 ohms for the TCC PWM solenoid.
    2. ⇒If the resistance is not within the specified range, remove the affected solenoid.
  2. Disconnect the wiring harness connector from the affected solenoid. Measure the resistance of the affected control circuit. The resistance should be between 19-31 ohms for the 1-2 SS and the 2-3 SS. The resistance should be between 10-15 ohms for the TCC PWM solenoid.
    3. ⇒If the resistance is not within the specified range, replace the affected solenoid.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Control and Shift Solenoids Replacement
    •  Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness
    •  Control Module References for TCM replacement, setup and reprogramming