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 P0961: Line Pressure Control (PC) Solenoid System Performance

### Circuit/System Description

The pressure control (PC) solenoid valve is an electronic device that regulates transmission line pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve. The transmission control module (TCM) controls the PC solenoid valve by applying a varying amount of amperage to the solenoid. The applied amperage can vary from 0.1-1.1 amps. Low amperage, 0.1 amp, indicates high line pressure. High amperage, 1.1 amps, indicates low line pressure. The duty cycle of the PC solenoid valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time, non-energized, or no current flow. Approximately 60 percent at idle indicates maximum ON time, energized, or high current flow. The TCM determines the appropriate line pressure for a given load by comparing the throttle position sensor voltage, the engine speed and other inputs.

### Conditions for Running the DTC

• | The system voltage is 8-18 volts.

• | The engine is running.

### Conditions for Setting the DTC

The PC solenoid valve duty cycle reaches its high limit, approximately 95 percent, or low limit, approximately 1.9 percent.

### Action Taken When the DTC Sets

• | DTC P0961 is a Type C DTC.

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

### Conditions for Clearing the DTC

DTC P0961 is a Type C DTC.

### Diagnostic Aids

DTC P0961 may set under low voltage conditions caused by high electrical system demands.

### 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, select PC Solenoid under the Transmission Output Controls. With the scan tool, command several values of solenoid reference current from 0.1 amp through 1.1 amps and observe the PC Sol. Actual Current and the PC Sol. Ref. Current. The PC Sol. Actual Current should not vary from the PC Sol. Ref. Current by more than 0.16 amps.

### Circuit/System Testing

1. Disconnect the AT inline 20-way connector. Install the J 44152 jumper harness (20 pins), on the transmission side on the connector. Using the J 35616 GM-approved terminal test kit, measure the resistance between the PC solenoid high control circuit and the PC solenoid low control circuit. The resistance should be between 3-7 ohms.

⇒ | If the resistance is greater than 7 ohms, test the PC solenoid high control circuit or the PC solenoid low control circuit for an open or a faulty PC solenoid valve.

⇒ | If the resistance is less than 3 ohms, test for the PC solenoid high control circuit and the PC solenoid low control circuit shorted together of a faulty PC solenoid valve.

2. Measure the resistance between the PC solenoid high control circuit and the transmission case. Measure the resistance between the PC solenoid low control circuit and the transmission case. The resistance should be greater than 250K ohms.

⇒ | If the resistance is less than 250K ohms, replace the automatic transmission wiring harness assembly.

3. Measure the resistance between the PC solenoid high control circuit and all other circuits of the J 44152 except the PC solenoid low control circuit. Measure the resistance between the PC solenoid low control circuit and all other circuits of the J 44152 except the PC solenoid high control circuit. The resistance should be greater than 250K ohms.

⇒ | If the resistance is less than 250K ohms, replace the automatic transmission wiring harness assembly.

4. Remove the J 44152 from the transmission side and install on the engine side of the harness. Disconnect the TCM connector. Using the J 35616 , measure the resistance of the PC solenoid high control circuit between the TCM connector and the AT inline 20-way connector. Measure the resistance of the PC solenoid low control circuit between the TCM connector and the AT inline 20-way connector. The resistance should be less than 250 ohms for each circuit.

⇒ | If the value is greater than 250 ohms, repair the open in the affected circuit.

5. Measure the resistance between the PC solenoid high control circuit and ground. Measure the resistance between the PC solenoid low control circuit and ground. The resistance for each circuit should be greater than 250K ohms.

⇒ | If the value is less than 250K ohms, repair the short to ground in the affected circuit.

6. Reconnect the TCM connector. Turn ON the ignition with the engine OFF. Test the PC solenoid high control circuit and the PC solenoid low control circuit for a short to voltage.

⇒ | If a short to voltage condition is found, repair as necessary.

⇒ | If all circuits/connections test normal, test or replace the PC solenoid valve.

### Component Testing

Verify the PC solenoid valve resistance is between 3-7 ohms.

⇒ | If the resistance is not within the specified range, replace the PC solenoid valve.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• | Control and Shift Solenoids Replacement

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