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4L60-E/4L65-E/4L70-E - Automatic Transmission




DTC P0961

Diagnostic Instructions

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

DTC Descriptor
DTC P0961
- Line Pressure Control (PC) Solenoid System Performance

Diagnostic Fault Information





Circuit/System Description

The pressure control (PC) solenoid valve is an electronic device located in the valve body. The transmission control module (TCM) controls transmission line pressure by regulating the current flow through the PC solenoid valve windings. The TCM determines the appropriate line pressure for a given load by monitoring the throttle position sensor voltage, the engine speed and other inputs. The TCM then varies the duty cycle on the high side of the PC solenoid valve to control current flow to the solenoid. The magnetic field produced by the coil moves the solenoids internal valve which varies pressure to the pressure regulator valve. The 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. Current is controlled from about 0.02 amp for maximum line pressure to 1.1 amps for minimum line pressure. The TCM monitors the actual current to the solenoid as compared to the requested or reference current.

Conditions for Running the DTC

* The system voltage is 8-18 volts.
* Engine running.
* PC solenoid valve enabled.

Conditions for Setting the DTC

The PC solenoid duty cycle is outside the range of 0.5-95 percent for 4 seconds.

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

* Low voltage conditions caused by high electrical system demands may cause DTC P0961 to set.
* The transmission drain plug is a good under vehicle ground point.

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (4L60-E/4L65-E/4L70-E - Automatic Transmission)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Transmission General Information (Transmission General Information)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

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

Transmission Control Module Scan Tool Information (4L60-E) (Transmission Control Module Scan Tool Information (4L60-E)) Transmission Control Module Scan Tool Information (6L45/6L50/6L80/6L90) (Transmission Control Module Scan Tool Information (6L45/6L50/6L80/6L90))
Special Tools

* EL-49741 9 V+ Power Source Harness
* EL-49742 Battery Voltage B+ and Ground Source Harness
* J 35616 GM-Approved Terminal Test Kit
* J 44152 Jumper Harness (20 pins)
* J 44257 Main Wiring Harness Connector Remover

Circuit/System Verification

1. Start and idle the engine.
2. Using a scan tool, select PC Solenoid under the Special Functions.
3. While monitoring the PC Sol. Actual Current and the PC Sol. Ref. Current parameters, command the PC solenoid reference current from 0.1 amps through 1.1 amps. The PC Sol. Actual Current should not vary from the PC Sol. Ref. Current by more than 0.16 amps.

Circuit/System Testing

1. Key OFF. Using the Main Wiring Harness Connector Remover J 44257, disconnect the automatic transmission (AT) inline 20-way connector.
2. Install the jumper harness J 44152 (20 pins) on the engine side of the harness.
3. Key ON, engine OFF.
4. Using the BN probe J 35616-6, test for a diagnostic B+ (+0.0/-1.0 V) between the PC Solenoid Valve High Control circuit, jumper harness pin C and a good ground.

• If the voltage tests less than the specified value, test the PC Solenoid Valve High Control circuit for an open/high resistance or a short to ground. If all circuits and connections test normal, test the TCM for proper operation.

5. Using the BN probe J 35616-6, test for a diagnostic B+ (+0.0/-1.0 V) between the PC Solenoid Valve High Control circuit, jumper harness pin C and the PC Solenoid Valve Low Control circuit, jumper harness pin D.

• If the voltage tests less than the specified value, test the PC Solenoid Valve Low Control circuit for an open/high resistance, short to ground or short to voltage. If all circuits and connections test normal, test the TCM for proper operation.

6. Using the BN probe J 35616-6, connect a test light between the PC Solenoid Valve High Control circuit, jumper harness pin C and a good ground. The test light should NOT illuminate or illuminate dully.

• If the test light illuminates brightly, test the PC Solenoid Valve High Control circuit for a short to voltage. If all circuits and connections test normal, test the TCM for proper operation.

7. Using the BN probe J 35616-6, connect a test light between the PC Solenoid Valve Low Control circuit, jumper harness pin D and the Ignition Voltage circuit, jumper harness pin E. The test light should NOT illuminate.

• If the test light illuminates brightly, test the PC Solenoid Valve Low Control circuit for a short to ground. If all circuits and connections test normal, test the TCM for proper operation.

8. Remove the jumper harness J 44152 (20 pins) from the engine side of the harness and install it on the transmission 20-way pass-thru connector.
9. Using the BN probes J 35616-6, test for 2-8 ohm between PC Solenoid Valve High Control circuit, jumper harness pin C and the PC Solenoid Valve Low Control circuit, jumper harness pin D.

• If the resistance is greater than the specified range, test the affected circuits for an open/high resistance. If all circuits and connections test normal, test the PC Solenoid Valve for proper operation.

• If the resistance is less than the specified range, test the affected circuit for a short together condition. If all circuits and connections test normal, test the PC solenoid Valve for proper operation.

10. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve High Control circuit, jumper harness pin C and all other pins of the jumper harness except the PC Solenoid Valve Low Control circuit, jumper harness pin D.

• If the resistance is less than the specified value, test the affected circuits for a shorted together condition. If all circuits and connections test normal, test the PC Solenoid Valve for proper operation.

11. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve High Control circuit, jumper harness pin C and the transmission case.

• If the resistance is less than the specified value, test the affected circuit for a short to the transmission case. If all circuits and connections test normal, test the PC Solenoid Valve for proper operation.

12. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve Low Control circuit, jumper harness pin D and all other pins of the jumper harness except the PC Solenoid Valve High Control circuit, jumper harness pin C.

• If the resistance is less than the specified value, test the affected circuits for a shorted together condition. If all circuits and connections test normal, test the PC Solenoid Valve for proper operation.

13. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve Low Control circuit, jumper harness pin D and the transmission case.

• If the resistance is less than the specified value, test the affected circuit for a short to the transmission case. If all circuits and connections test normal, test the PC Solenoid Valve for proper operation.

14. Go to TCM testing.

Component Testing

PC Solenoid Valve
1. Key OFF. Using the Main Wiring Harness Connector Remover J 44257, disconnect the automatic transmission (AT) inline 20-way connector.
2. Install the jumper harness J 44152 (20 pins) on the transmission 20-way pass-thru connector.
3. Using the BN probes J 35616-6, test for 2-8 ohm between PC Solenoid Valve High Control circuit, jumper harness pin C and the PC Solenoid Valve Low Control circuit, jumper harness pin D.

• If the resistance is greater than the specified range, test the affected circuits for an open/high resistance. If all circuits and connections test normal, replace the PC Solenoid Valve.

• If the resistance is less than the specified range, test the affected circuit for a short together condition. If all circuits and connections test normal, replace the PC Solenoid Valve.

4. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve High Control circuit, jumper harness pin C and all other pins of the jumper harness except the PC Solenoid Valve Low Control circuit, jumper harness pin D.

• If the resistance is less than the specified value, test the affected circuits for a shorted together condition. If all circuits and connections test normal, replace the PC Solenoid Valve.

5. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve High Control circuit, jumper harness pin C and the transmission case.

• If the resistance is less than the specified value, test the affected circuit for a short to the transmission case. If all circuits and connections test normal, replace the PC Solenoid Valve.

6. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve Low Control circuit, jumper harness pin D and all other pins of the jumper harness except the PC Solenoid Valve High Control circuit, jumper harness pin C.

• If the resistance is less than the specified value, test the affected circuits for a shorted together condition. If all circuits and connections test normal, replace the PC Solenoid Valve.

7. Using the BN probes J 35616-6, test for greater than 250K ohm between PC Solenoid Valve Low Control circuit, jumper harness pin D and the transmission case.

• If the resistance is less than the specified value, test the affected circuit for a short to the transmission case. If all circuits and connections test normal, replace the PC Solenoid Valve.

TCM
1. Circuit/System Testing must be performed before testing the TCM.
2. Connect the automatic transmission (AT) inline 20-way connector to the transmission 20-way pass-thru connector.
3. Start and idle the engine.
4. Using a scan tool, select PC Solenoid under the Special Functions.
5. While monitoring the PC Sol. Actual Current and the PC Sol. Ref. Current parameters, command the PC solenoid reference current from 0.1 amps through 1.1 amps. The PC Sol. Actual Current should not vary from the PC Sol. Ref. Current by more than 0.16 amps.

• If the PC Sol. Actual Current varies more than the specified value, replace the TCM.

Repair Instructions

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

* Control and Shift Solenoids Replacement (4L60-E/4L65-E/4L70-E - Automatic Transmission)
* Control Module References (Programming and Relearning) for TCM replacement, setup, and programming.

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