Diagnostic Instructions

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

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	Open	Short to Volts
2-3 Sol. CKT Status	Indeterminate	Short to GND	Open	Short to Volts
TCC Duty Cycle CKT Status	Indeterminate	Short to GND	Open	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 P0973 and DTC P0976

The ignition is ON.

DTC P2764

The engine is running 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

DTC P0973

DTC P0976

DTC P2764

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 1-2 SS, 2-3 SS, and TCC PWM solenoid ON and OFF. Observing the CKT Status parameter on the scan tool, ensure 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 automatic transmission inline 20-way connector.

2. Disconnect the automatic transmission inline 20-way connector. Connect the J 44152 jumper harness (20 pins) to the engine side of the connector. Using the J 35616 GM 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.

3. Connect the J 44152 jumper harness (20 pins) to the transmission side of the connector. Using the J 35616 GM terminal test kit, 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 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 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.