GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Silverado - 4WD 🢒 DTC 🢒 DTC P0963

Circuit Description

The pressure control solenoid (PCS) main modulation (MAIN MOD) is a normally closed (N/C) solenoid used to modulate transmission main pressure. The transmission control module (TCM) commands the solenoid ON when specific transmission and engine conditions are met. When solenoid MAIN MOD is commanded ON, hydraulic pressure is routed to the main pressure regulator valve, lowering transmission main pressure.

The TCM provides voltage to the MAIN MOD, torque converter clutch (TCC) and pressure control solenoid 1 (PCS1) through a separate solid-state device called high side driver 1 (HSD1). The TCM uses a low side driver to switch MAIN MOD ON and OFF.

DTC P0963 is a type A DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0963 Pressure Control Solenoid (PCS) Main Modulation (MAIN MOD) Circuit High

Conditions for Running the DTC
    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • TCM initialization is in process or engine speed is greater than 200 RPM and less than 7,500 RPM for less than 5 seconds.
    • The TCM must auto-detect the MAIN MOD solenoid for this test to run.

Conditions for Setting the DTC

DTC P0963 sets when the TCM detects a short to voltage in the MAIN MOD solenoid return circuit for greater than 2 seconds.

Action Taken When the DTC Sets
    • The TCM illuminates the malfunction indicator lamp (MIL).
    • DTC P0963 is stored in TCM history.
    • The TCM inhibits MAIN MOD.

Conditions for Clearing the MIL/DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
    • Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
       - A bent terminal
       - A backed-out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • You may have to drive the vehicle in order to experience a condition.

Step

Action

Value

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Using the scan tool, measure ignition voltage.

Is voltage within the specified value?

9-18 V

Go to Step 3

Go to DTC P0562 for low voltage or DTC P0563 for high voltage

3

  1. Turn the ignition OFF.
  2. Disconnect the 80-way connector at the TCM.
  3. Install the J 39700 breakout box, the J-47275 breakout box adapter and the J 47275-1 magnetic overlay.
  4. Turn ON the ignition, with the engine OFF.
  5. Using the DMM, measure voltage between connector terminal 74 and ground.
  6. Using the scan tool, command MAIN MOD solenoid ON.

Is the voltage within the specified value when the MAIN MOD solenoid is commanded ON?

Less than battery voltage

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the TCM from the J 39700 . Additional DTCs may set.
  3. Turn ON the ignition, with the engine OFF.
  4. Using the DMM, measure voltage at terminal 74 and ground.

Is the voltage greater than the specified value?

0 V

Go to Step 5

Go to Testing for Intermittent Conditions and Poor Connections

5

  1. Turn the ignition OFF.
  2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
  3. Install the J 44152 jumper harness (20 pins) on the engine side of the AT inline 20-way connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Using the DMM and the J 35616 GM terminal test kit, measure for voltage at terminal S and ground of the J 44152 . Refer to Inline Harness Connector End Views .

Is the voltage greater than the specified value?

0 V

Go to Step 8

Go to Step 6

6

  1. Connect the AT inline 20-way connector.
  2. Remove the transmission oil pan. Refer to Oil Pan Replacement .
  3. Remove the AT internal wiring harness at the MAIN MOD connector.
  4. Using the DMM, measure for voltage at terminal 2 of the MAIN MOD solenoid and ground.

Is the voltage greater than the specified value?

0 V

Go to Step 9

Go to Step 7

7
  1. Disconnect the torque converter clutch pressure control solenoid (TCC PCS) from the internal wiring harness.
  2. Using the DMM, measure MAIN MOD solenoid resistance.

Is resistance within the specified value?

5.05 ohms at 20°C (68°F)

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 10

8

Test the MAIN MOD solenoid circuit between the TCM and the AT inline 20-way connector for a short to voltage. Refer to Testing for a Short to Voltage .

Did you find and correct the condition?

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Go to Step 11

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9

Replace the AT internal wiring harness. Refer to Wiring Harness Replacement .

Did you complete the replacement?

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Go to Step 11

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10

Replace the MAIN MOD solenoid. Refer to Control Valve Solenoid Replacement .

Did you complete the replacement?

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Go to Step 11

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11

Perform the following procedure in order to verify the repair:

  1. Clear the DTC.
  2. Drive the vehicle under normal operating conditions.
  3. Select Specific DTC.
  4. Enter DTC P0963.

Has the test run and passed?

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Go to Step 12

Go to Step 2

12

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

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

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Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK