GM Service Manual Online
For 1990-2009 cars only

Object Number: 1651677  Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Control Module References

Circuit Description

The pressure control (PC) solenoid valve is located in the valve body. The PC solenoid valve controls transmission line pressure based on current flow through its windings. The transmission control module (TCM) determines desired line pressure based on throttle position 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. Current is controlled from about 0.02 amps for maximum line pressure to 1.1 amps for minimum line pressure. The TCM monitors the actual current to the solenoid.

If the TCM detects a commanded current draw that differs from the actual current draw by more than a calibrated value, then DTC P0961 sets. DTC P0961 is a type C DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0961 Line Pressure Control (PC) Solenoid System Performance

Conditions for Running the DTC

The PC solenoid valve is enabled.

Conditions for Setting the DTC

DTC P0961 sets when the duty cycle is outside the range of 0.5-95 percent for 0.2 seconds.

Action Taken When the DTC Sets

    • The TCM does not request the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
    • The TCM stores DTC P0961 in TCM history.

Conditions for Clearing the DTC

    • The TCM clears the DIC message when the condition no longer exits.
    • A scan tool can clear the DIC/DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step verifies that the fault is present.

  2. This step tests the transmission wiring harness and the PC solenoid valve for correct resistance.

  3. This step begins diagnosis of the engine side of the circuit.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Start the engine.
  3. Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the TCM.

  4. Record the Failure Records.
  5. Clear the DTCs.
  6. With the scan tool, command several values of solenoid reference current from 0.1 amp through 1.1 amp and observe the scan tool display.

Does the PC Sol. Actual Current reading vary from the PC Sol. Ref. Current reading by more than the specified amount?

0.16 amp

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

  1. Turn OFF the ignition.
  2. Disconnect the transmission 20-way connector, additional DTCs may set.
  3. Connect the J 44152 jumper harness to the transmission side of the 20-way connector.
  4. Using the J 35616 GM terminal test kit, connect a DMM between the PC solenoid valve high control circuit and low control circuits of the J 44152 .
  5. Refer to Automatic Transmission Inline 20-Way Connector End View .

  6. Measure the resistance of the PC solenoid valve.

Does the resistance measure within the specified range?

3-7 ohms

Go to Step 7

Go to Step 4

4

Is the resistance greater than the specified value?

7 ohms

Go to Step 5

Go to Step 6

5

  1. Test the high control circuit of the PC solenoid valve for an open between the AT inline 20-way connector and the PC solenoid valve.
  2. Test the low control circuit of the PC solenoid valve for an open between the AT inline 20-way connector and the PC solenoid valve.

Refer to Testing for Continuity .

Did you find the condition?

--

Go to Step 15

Go to Step 14

6

Test the high control circuit and the low control circuit of the PC solenoid valve for a short together between the AT inline 20-way connector and the PC solenoid valve.

Refer to Circuit Testing .

Did you find the condition?

--

Go to Step 15

Go to Step 14

7

  1. Test the high control circuit of the PC solenoid valve for a short to the transmission case between the AT inline 20-way connector and the PC solenoid valve.
  2. Test the high control circuit of the PC solenoid valve for a short to other power and ground circuits in the transmission harness. Test from the PC solenoid valve high control circuit to all other terminals in the transmission 20-way connector.

Refer to:

    •  Circuit Testing

Did you find the condition?

--

Go to Step 15

Go to Step 8

8

  1. Test the low control circuit of the PC solenoid valve for a short to the transmission case between the AT inline 20-way connector and the PC solenoid valve.
  2. Test the low control circuit of the PC solenoid valve for a short to other power and ground circuits in the transmission harness. Test from the PC solenoid valve low control circuit to all other terminals in the transmission 20-way connector.

Refer to:

    •  Circuit Testing

Did you find the condition?

--

Go to Step 15

Go to Step 9

9

  1. Disconnect the J 44152 from the transmission side of the 20-way connector.
  2. Reconnect the 20-way connector.
  3. Disconnect the TCM connector.
  4. Using the DMM, measure the resistance between the PC solenoid valve high control and low control circuits of the TCM harness connector.

Does the resistance measure within the specified range?

3-7 ohms

Go to Step 13

Go to Step 10

10

Does the resistance measure greater than the specified value?

7 ohms

Go to Step 11

Go to Step 12

11

  1. Test the high control circuit of the PC solenoid valve for an open between the TCM and the AT inline 20-way connector.
  2. Test the low control circuit of the PC solenoid valve for an open between the TCM and the AT inline 20-way connector.

Refer to Testing for Continuity and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 17

--

12

Test the high control circuit and the low control circuit of the PC solenoid valve for a short together between the TCM and the AT inline 20-way connector.

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 17

--

13

  1. Test the high control circuit of the PC solenoid valve for a short to ground or short to voltage between the TCM and the AT inline 20-way connector.
  2. Test the low control circuit of the PC solenoid valve for a short to ground or short to voltage between the TCM and the AT inline 20-way connector.

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 17

Go to Step 16

14

Replace the pressure control solenoid valve.

Refer to Control Valve Upper Body Disassemble in the 4T80-E section of the Transmission Unit Repair Manual.

Did you complete the replacement?

--

Go to Step 17

--

15

Replace the automatic transmission wiring harness assembly.

Refer to Input Speed Sensor and Wiring Harness Removal in the 4T80-E section of the Transmission Unit Repair Manual.

Did you complete the replacement?

--

Go to Step 17

--

16

Replace the TCM.

Refer to Control Module References .

Did you complete the replacement?

--

Go to Step 17

--

17

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Start the engine.
  4. The PC solenoid valve actual current must be between 0.1 and 1.1 amp.
  5. Select Specific DTC.
  6. Enter DTC P0961.

Has the test run and passed?

--

Go to Step 18

Go to Step 2

18

With a scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK