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 Descriptor

DTC P0974 : 1-2 Shift Solenoid (SS) Control Circuit High Voltage
DTC P0977: 2-3 Shift Solenoid (SS) Control Circuit High Voltage
DTC P0980: 4-5 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, 2-3 SS valve and the 4-5 SS valve control transmission fluid pressure acting on the shift valves to position the valves for the appropriate gear. The 1-2 SS, 2-3 SS and the 4-5 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. The TCM provides voltage to the solenoid through high side driver 2 (HSD2). When the 1-2 SS valve, 2-3 SS or the 4-5 SS valve is commanded ON, the TCM senses low voltage. When the 1-2 SS valve, 2-3 SS or the 4-5 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. The TCM provides voltage to the TCC PWM solenoid valve through HSD2. 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 run time is greater than 5 seconds.

• | HSD2 is commanded ON.

### Conditions for Setting the DTC

#### P0974

The TCM detects a short to voltage in the 1-2 shift solenoid valve circuit for 4.3 seconds.

#### P0977

The TCM detects a short to voltage in the 2-3 shift solenoid valve circuit for 4.3 seconds.

#### P0980

The TCM detects a short to voltage in the 4-5 shift solenoid valve circuit for 4.3 seconds.

#### P2763

The TCM detects a short to voltage in the TCC PWM solenoid valve circuit when the PWM duty cycle is 45 percent or greater for 4.3 seconds.

### Action Taken When the DTC Sets

#### P0974

• | DTC P0974 is a Type B DTC.

• | Powertrain braking is disabled at the time that the TCM first detects the failure, before the DTC sets.

• | The TCM commands HSD1 OFF.

• | The TCM inhibits 3-2 downshifts if the vehicle speed is 8 km/h (5 mph) or greater.

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

• | The TCM inhibits TAP shift.

#### P0977

• | DTC P0977 is a Type B DTC.

• | The TCM commands HSD1 OFF.

• | The TCM inhibits first gear.

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

• | The TCM inhibits TAP shift.

#### P0980

• | DTC P0980 is a Type B DTC.

• | Powertrain braking is disabled at the time that the TCM first detects the failure, before the DTC sets.

• | The TCM turns off power to all solenoids.

• | The transmission will operate in fifth gear if the vehicle has successfully completed a 1-2 upshift in the current ignition cycle. If the vehicle has not completed a 1-2 upshift in the current ignition cycle, the transmission will operate in fourth gear.

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

• | The TCM inhibits TAP shift.

#### P2763

• | DTC P2763 is a Type B DTC.

• | The TCM inhibits TCC.

• | The TCM inhibits fifth gear if the transmission is in Hot Mode.

• | The TCM freezes transmission adaptive functions.

### Conditions for Clearing the DTC

DTC P0974, P0977, P0980 and P2763 are Type B DTCs.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Transmission General Description

#### 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)

• | J 45681 Jumper Harness

### 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 45681 jumper harness, 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.

⇒ | 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 45681 from the engine harness. Connect the J 45681 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 15-20.3 ohms for the 1-2 SS, 2-3 SS and the 4-5 SS. Resistance should be between 10-13.6 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 , measure the resistance between the affected control circuit and all other circuits in the J 45681 except the ignition 1 voltage circuit and the other control circuits. Resistance should be greater than 50K ohms.

⇒ | If resistance is less than 50K ohms, test the control circuit for a short to another circuit.

### Component Testing

1. Using the J 44152 jumper harness (20 Pins), and the J 35616 measure the resistance between the ignition 1 voltage circuit and the affected control circuit. The resistance should be between 15-20.3 ohms for the 1-2 SS, 2-3 SS and the 4-5 SS. The resistance should be between 10-13.6 ohms for the TCC PWM solenoid.

⇒ | If the resistance is not within the specified range, remove the oil pan.

2. Disconnect the wiring harness connector from the affected solenoid. Measure the resistance of the affected control circuit. The resistance should be between 15-23.3 ohms for the 1-2 SS, 2-3 SS and the 4-5 SS. The resistance should be between 10-13.6 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.

• | 1-2 Shift Solenoid Valve Replacement

• | 2-3 Shift Solenoid Valve Replacement

• | 4-5 Shift Solenoid Valve Replacement

• | Torque Converter Clutch Solenoid Replacement

• | Transmission Internal Electrical Harness Replacement

• | Control Module References for TCM replacement, setup and reprogramming.