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Automatic Transmission - 4T80-E




DTC P0973, P0974, P0976, P0977, P2763, or P2764

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0973
- 1-2 Shift Solenoid (SS) Control Circuit Low Voltage

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

DTC P0976
- 2-3 Shift Solenoid (SS) Control Circuit Low 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

DTC P2764
- Torque Converter Clutch (TCC) Pressure Control (PC) Solenoid Control Circuit Low Voltage

Diagnostic Fault Information





Typical Scan Tool Data





Circuit/System Description

The 1-2 Shift and 2-3 Shift Solenoids

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.

Torque Converter Clutch (TCC) Solenoid

The torque converter clutch (TCC) pulse width modulated (PWM) solenoid is a normally closed solenoid used to control the apply and release of the converter clutch. When the vehicle operating conditions are appropriate to apply the TCC, the transmission control module (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 TCC is fully applied, the engine is coupled directly to the transmission through the TCC. 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

P0973, P0974, P0976 and P0977
* The ignition is ON.
* The ignition voltage is between 8 and 18 volts.

P2763
* The ignition voltage is between 8 and 18 volts.
* The engine speed is between 500 and 6,500 RPMs for 5 seconds.
* The TCC is commanded ON.

P2764
* The ignition voltage is between 8 and 18 volts.
* The engine speed is between 500 and 6,500 RPMs for 5 seconds.

Conditions for Setting the DTC

P0973 and P0976

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

P0974 and P0977

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

P2763

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

P2764

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

Action Taken When the DTC Sets

* DTCs P0973, P0974, P2763, and P2764 are Type B DTCs.
* DTCs P0976 and P0977 are Type A DTCs.

Conditions for Clearing the DTC

* DTCs P0973, P0974, P2763, and P2764 are Type B DTCs.
* DTCs P0976 and P0977 are Type A DTCs.

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning)
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, ensure the parameter shows OK.

Circuit/System Testing

1. Ignition OFF, disconnect the transmission 20-way harness connector.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal and ground.

* Terminal E for shift solenoid valve 1-2 and 2-3.
* Terminal U for the TCC solenoid.

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse is open, test or replace the affected solenoid.

3. Connect a test lamp between the control circuit terminal and the ignition voltage circuit terminal.

* Terminals E and A for shift solenoid valve 1-2.
* Terminals E and B for shift solenoid valve 2-3.
* Terminals U and T for the TCC solenoid.

4. Command the affected shift solenoid ON and OFF with a scan tool or command the TCC solenoid to 90 percent with a scan tool. The test lamp should respond when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the TCM.

• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the TCM.

5. If all circuits test normal, test or replace the internal transmission wiring harness or the affected solenoid.

Component Testing

Shift Solenoid Valves
1. Ignition OFF, disconnect the transmission harness connector.
2. Test for 19-24 ohms of resistance at 20°C (68°F) or 24-31 ohms of resistance at 88°C (188°F) between the ignition voltage terminal and the control terminal of the affected shift solenoid valve.

* Terminals E and A for shift solenoid valve 1-2.
* Terminals E and B for shift solenoid valve 2-3.

• If not within the specified range, test the internal transmission wiring harness for an open or high resistance. If the circuits test normal, replace the affected shift solenoid valve.

3. Test for infinite resistance between each terminal and ground.

• If not the specified value, test the internal transmission wiring harness for a short to ground. If the circuits test normal, replace the affected shift solenoid valve.

TCC Solenoid
1. Ignition OFF, disconnect the transmission harness connector.
2. Test for 10-12 ohms of resistance at 20°C (68°F) or 13-15 ohms of resistance at 88°C (188°F) between the ignition voltage terminal U and the control terminal T of the TCC solenoid.

• If not within the specified range, test the internal transmission wiring harness for an open or high resistance. If the circuits test normal, replace the TCC solenoid.

3. Test for infinite resistance between each terminal and ground.

• If not the specified value, test the internal transmission wiring harness for a short to ground. If the circuits test normal, replace the TCC solenoid valve.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the repair.

* Control Valve Lower Body Disassemble (Overhaul)
* Control Valve Upper Body Disassemble (Overhaul)
* Control Module References (Programming and Relearning) for TCM replacement, setup and reprogramming

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