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P0976



DTC P0973, P0976, or P2764

DTC Descriptors

* DTC P0973 1-2 Shift Solenoid (SS) Control Circuit Low Voltage
* DTC P0976 2-3 Shift Solenoid (SS) Control Circuit Low Voltage
* DTC P2764 Torque Converter Clutch (TCC) Pressure Control (PC) Solenoid Control Circuit Low Voltage

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview








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 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 normally closed solenoid used to control the apply and release of the converter clutch. The 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

The engine speed is greater than 500 RPM for 5 seconds.

Conditions for Setting the DTC

DTC P0973

The TCM detects an open or short to ground on the 1-2 SS valve control circuit for 4.4 seconds.

DTC P0976

The TCM detects an open or short to ground on the 2-3 SS valve control circuit for 4.4 seconds.

DTC P2764

The TCM detects an open or short to ground on the TCC PWM solenoid valve control circuit for 4.4 seconds.

Action Taken When the DTC Sets

* DTCs P0973 and P2764 are Type B DTCs.
* DTC P0976 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.

DTC P0973

The TCM inhibits 3-2 downshifts when the vehicle speed is greater than 52 km/h (32 mph).

DTC P0976

The TCM commands a soft landing to 2nd gear.

DTC P2764

* 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 P0973 and P2764 are Type B DTCs.
* DTC P0976 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 1-2 SS ON and OFF. Observing the 1-2 Sol. CKT Status parameter on the scan tool, ensure that the parameter shows OK.

Circuit/System Testing

1. Inspect the TRANS fuse for an open.
- If the fuse is open, test the ignition 1 voltage circuit and the affected control circuit for a short to ground between the Fuse Block-Underhood and the AT inline 20-way connector.

2. Disconnect the AT inline 20-way connector. Connect the J 44152 to the engine side of the connector. Using the J 35616, connect a test lamp between the ignition 1 voltage circuit and the affected control circuit. Turn On the ignition with the engine OFF. Using the scan tool output controls command the affected solenoid ON and OFF. The test lamp should blink ON and OFF as commanded.
- If the test lamp is always OFF, test the circuits for an open.

3. Connect the J 44152 to the transmission side of the connector. Using the J 35616, measure the resistance between the ignition 1 voltage circuit and the affected control 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.
- If resistance is greater than the specified range, test the circuits for an open. If the resistance is less than the specified range, test for a faulty solenoid or a shorted together condition.

4. Measure the resistance between the ignition 1 voltage circuit and the transmission case. The resistance should be greater than 10K ohms.
- If the resistance is less than 10K ohms, test the ignition 1 voltage circuit for a short to ground.

5. Measure the resistance between the affected control circuit and ground. The resistance should be greater than 10K ohms.
- If the resistance is greater than 10K ohms, test the affected control circuit for a short to ground.

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.
- 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 19-31 ohms for the 1-2 SS and the 2-3 SS. The resistance should be between 10-15 ohms for the TCC PWM solenoid.
- If the resistance is not within the specified range, replace the affected solenoid.

Repair Instructions

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
* Control Valve Body Cover Removal and Side Cover/Gaskets, Disassemble, Assemble, Install in Transmission Unit Repair.
* Programming and Relearning. Programming and Relearning
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