Diagnostic Instructions

DTC Descriptors

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

Circuit	Short to Ground	Open/High Resistance	Short to Voltage
Ignition 1 Voltage	P0973, P0976, P2764	P0973, P0976, P2764	--
1-2 SS Valve control	P0973	P0973	P0974
2-3 SS Valve Control	P0976	P0976	P0977
TCC PWM Valve Control	P2764	P2764	P2763

Typical Scan Tool Data

Circuit	Normal	Short to Ground	Open/High Resistance	Short to Voltage
Operating Conditions: Engine running, normal operating temperature Parameter Normal Range: Indeterminate
1-2 Sol. CKT Status	Indeterminate	Short to GND	Short to GND	Short to Volts
2-3 Sol. CKT Status	Indeterminate	Short to GND	Short to GND	Short to Volts
TCC Duty Cycle CKT Status	Indeterminate	Short to GND	Short to GND	Short to Volts

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

DTC P0974 and DTC P0977

The ignition is ON.

DTC P2763

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

DTC P0974

DTC P0977

DTC P2763

Conditions for Clearing the DTC

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

DTC Type Reference

Special Tools Required

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 the parameter displays OK.

Circuit/System Testing

1. Disconnect the automatic transmission inline 20-way connector. Install the J 44152 jumper harness (20 pins) on the engine side of the automatic transmission 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 automatic transmission inline 20-way connector.

2. Disconnect the J 44152 jumper harness (20 pins) from the engine harness. Connect the J 44152 jumper harness (20 pins) to the transmission side of the automatic transmission 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 19-31 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 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 (20 pins), 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 (20 pins) 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 19-31 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.