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P0974



DTC P0974, P0977, or P2763

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

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview




Scan Tool Parameter Data:





Circuit/System Description

The 1-2 shift solenoid (SS) valve and the 2-3 SS valves 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 normally-open exhaust valves located on the control valve body. A fused circuit supplies ignition voltage to the 1-2 SS valve and the 2-3 SS valve. The 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 normally closed solenoid used to control the apply and release of the converter clutch. The transmission control module (TCM) operates the solenoid with a negative duty cycle. When vehicle operating conditions are appropriate to apply the TCC, the TCM immediately increases the duty cycle to approximately 42 percent. The TCM then ramps the duty cycle to approximately 90 percent to achieve full TCC apply pressure. 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

DTC P0974 and DTC P0977

The ignition is ON.

DTC P2763
* The engine is running for 5 seconds.
* The TCC PWM solenoid is commanded ON.

Conditions for Setting the DTC

DTC P0974

The TCM detects a short to voltage on the 1-2 SS valve control circuit for 4.4 seconds.

DTC P0977

The TCM detects a short to voltage on the 2-3 SS valve control circuit for 4.4 seconds.

DTC P2763

The TCM detects a short to voltage on the TCC PWM solenoid valve control circuit for 4.4 seconds.

Action Taken When the DTC Sets

* DTCs P0974 and P2763 are Type B DTCs.
* DTC P0977 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.

DTC P0977

The TCM inhibits 4th gear.

DTC P2763
* The TCM forces the TCC solenoid OFF.
* The TCM inhibits TCC engagement.
* The TCM inhibits 4th gear when in HOT mode.

Conditions for Clearing the DTC

* DTCs 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
* Automatic Transmission Inline 20-Way Connector End View
* Automatic Transmission Internal Connector End Views
* Automatic Transmission Related Connector End Views

Electrical Information Reference
* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs

Scan Tool Reference
* Scan Tool Data List
* Scan Tool Data Definitions
* Scan Tool Output Controls

DTC Type Reference
* Diagnostic Trouble Code (DTC) Type Definitions
* Diagnostic Trouble Code (DTC) List/Type

Special Tools Required
* J 35616 GM 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 displays OK.

Circuit/System Testing

1. Disconnect the AT inline 20-way connector. Install the J 44152 jumper harness on the engine side of the AT inline 20-way connector. Using the J 35616 GM 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.

^ 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 jumper harness from the engine harness. Connect the J 44152 jumper harness to the transmission side of the AT inline 20-way connector. Using the J 35616 GM terminal test kit, measure the resistance between the affected control circuit and the ignition 1 voltage circuit. Resistance should be between 19 and 31 ohms for the 1-2 SS and the 2-3 SS. Resistance should be between 10 and 15 ohms for the TCC PWM solenoid valve.

^ 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 GM terminal test kit, measure the resistance between the affected control circuit and all other circuits in the J 44152 jumper harness except the ignition 1 voltage circuit and the other control circuits. Resistance should be greater than 10 ohms.

^ If resistance is less than 10 ohms, test the control circuit for a short to another circuit.

Component Testing

1. Using the J 44152 jumper harness and the J 35616 GM terminal test kit measure the resistance between the ignition 1 voltage circuit and the affected control circuit. The resistance should be between 19 and 31 ohms for the 1-2 SS and the 2-3 SS. The resistance should be between 10 and 15 ohms for the TCC PWM solenoid.

^ If the resistance is not within the specified range, remove the case side cover.

2. Disconnect the wiring harness connector from the affected solenoid. Measure the resistance of the affected control circuit. The resistance should be between 19 and 31 ohms for the 1-2 SS and the 2-3 SS. The resistance should be between 10 and 15 ohms for the TCC PWM solenoid.

^ If the resistance is not within the specified range, replace the affected solenoid.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the repair. Verification Tests

1-2 Shift Solenoid Valve Replacement

2-3 Shift Solenoid Valve Replacement

Torque Converter Clutch Pulse Width Modulation Solenoid Replacement

Case Cover Removal, Case Cover and Gaskets Assemble and Case Cover Components Disassemble (Without Touch Activated Power) Case Cover Components Disassemble (With Touch Activated Power)

Programming and Relearning Programming and Relearning

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