For 1990-2009 cars

### 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 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

### 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

#### P0973

• | The TCM detects an open in the 1-2 shift solenoid valve circuit when commanded ON.

• | The TCM detects a short to ground in the 1-2 shift solenoid valve circuit when commanded OFF.

#### P0976

• | The TCM detects an open in the 2-3 shift solenoid valve circuit when commanded ON.

• | The TCM detects a short to ground in the 2-3 shift solenoid valve circuit when commanded OFF.

#### P2764

• | The TCM detects an open in the TCC PWM solenoid valve circuit when the TCC PWM is commanded ON.

• | The TCM detects a short to ground in the TCC PWM solenoid valve circuit when the TCC PWM is commanded ON.

### Action Taken When the DTC Sets

#### P0973

• | DTC P0973 is a Type B DTC.

• | The TCC commands maximum line pressure.

• | The TCM inhibits 3-2 shift until vehicle speed is less than 20 km/h (12 mph).

• | The TCM freezes transmission adaptive functions.

#### P0976

• | DTC P0976 is a Type A DTC.

• | The TCM inhibits 1st and 4th gear.

• | The TCC commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

#### P2764

• | DTC P2764 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 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

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 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 jumper harness (20 Pins), to the engine side of the connector. Using the J 35616 GM-approved terminal test kit, 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.

⇒ | If the test lamp is always ON, test the circuits for a short to ground.

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 250K ohms.

⇒ | If the resistance is less than 250K 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 less than 250K ohms.

⇒ | If the resistance is greater than 250K 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 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.

⇒ | 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