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For 1990-2009 cars only
Makes 🢒 Holden 🢒 2005 🢒 Commodore Berlina 🢒 DTC 🢒 DTC P0787

DTC P0787 V6

DTC Description

This diagnostic procedure supports the following DTC:

DTC P0787 3-2 Shift Solenoid (SS) Control Circuit Low Voltage

Circuit Description

The 3-2 shift solenoid (SS) valve is a normally-closed, 3-port, on/off device that controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. The solenoid receives ignition voltage through the ignition 1 circuit (circuit 339). The transmission control module (TCM) controls the solenoid by providing a ground path on the 3-2 shift solenoid valve control circuit (circuit 687). During a 3-2 downshift, the 2-4 band applies as the 3-4 clutch releases. The TCM varies the timing between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and the throttle position.

When the TCM detects a continuous open or short to ground in the 3-2 SS valve circuit, then DTC P0787 sets.

Refer to Automatic Transmission Controls Schematics , Automatic Transmission Inline 20-Way Connector End View , Automatic Transmission Internal Connector End Views , Automatic Transmission Control Module Connector End Views , and Automatic Transmission Related Connector End Views to aid in diagnosis.

Conditions for Running the DTC
    • The system voltage is 10-18 V.
    • The engine speed is greater than 450 RPM for 5 seconds.
    • Vehicle speed is less than 200 km/h.

Conditions for Setting the DTC

The TCM commands the solenoid off and the voltage feedback remains low, 0 V.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the check powertrain icon during the second consecutive trip in which the conditions for setting the DTC are met.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The TCM commands 3rd gear.
    • The TCM inhibits TCC engagement.
    • At the time of the first failure, the TCM records the operating conditions when the conditions for setting the DTC are met. The TCM stores this information as a Failure Record.
    • At the time of the first failure, the ECM records the operating conditions when the conditions for setting the DTC are met. The ECM stores this information as a Freeze Frame.
    • The TCM stores DTC P0787 in TCM history during the second consecutive trip in which the conditions for setting the DTC are met.

Conditions for Clearing the DTC
    • The ECM turns off the check powertrain icon after the fourth consecutive drive trip in which the TCM does not send a check powertrain icon illumination request.
    • Tech 2 can clear the 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 ignition is off long enough in order to power down the TCM

Test Description

The following numbers refer to the step numbers on the diagnostic table:

  1. Checks the ability of the TCM to control the solenoid.
  2. Checks for supply voltage to the 3-2 SS valve.
  3. Checks the ability of the TCM and wiring to control the ground circuit.
  4. Checks the resistance of the control valve body wiring harness and the 3-2 SS valve.
  5. Checks if the 3-2 SS or control valve body wiring harness is shorted to the transmission housing.
  6. Checks if the control valve body wiring harness is shorted to ground.
  7. Checks is any of the other solenoids in the transmission are shorted to ground.

Step

Action

Yes

No

1

Has the Diagnostic System Check been performed?

Go to Step 2

Refer to Diagnostic System Check - Automatic Transmission

2
  1. Connect Tech 2 to the DLC.
  2. Turn on the ignition, with the engine off.

    3. Important: Before clearing the DTC, use the Tech 2 Freeze Frame/Failure Record in order to record the transmission parameters at the time the DTC set. Using Tech 2 to clear the DTC(s) erases the Freeze Frame/Failure Record records from the TCM.

  3. On Tech 2 select:

    4. Transmission / Automatic Transmission / Diagnostic Trouble Codes / Freeze Frame.

  4. Select the relevant DTC and note the parameters at the time of the DTC setting.
  5. On Tech 2 select:

    6. Diagnostic Trouble Codes / Clear Engine and Transmission DTCs.

  6. Follow the instructions on Tech 2 and clear the DTCs.

Are any of the following DTCs also set?

    • P0961
    • P0973
    • P0976
    • P2764
    • P2769

Go to Step 3

Go to Step 4

3

Inspect fuse F8 and check if it is blown, refer to Section 12O Fuses, Relays and Wiring Harnesses.

Is the fuse blown?

Replace the fuse

Go to Step 12

Go to Step 5

4
  1. On Tech 2 select:

    2. Automatic Transmission / Miscellaneous Tests / 3-2 Downshift Solenoid.

  2. With Tech 2 command the 3-2 shift solenoid ON and OFF.

Does Tech 2 display the 3-2 Downshift Solenoid as Active and Inactive respectively?

Check for an intermittent fault in the circuit, refer to Testing for Intermittent Conditions and Poor Connections

Go to Step 5

5
  1. Turn off the ignition.
  2. Disconnect connector X121 -- X1 from the transmission.

    3. Important: Additional DTCs may set

  3. Install J 44152 Jumper Harness (20 pins on the harness connector X121 - X1.
  4. Turn on the ignition, with the engine off.
  5. Using a test lamp, probe between connector X121- X1 pin E and a known ground.

Does the test lamp illuminate?

Go to Step 6

Check circuit 339 for an open circuit

Repair or replace circuit 339

Go to Step 18

6
  1. Using a test lamp, probe connector X121- X1 pin E with the ground lead to connector X121 - X1 pin S.
  2. On Tech 2 select:

    3. Automatic Transmission / Miscellaneous Tests / 3-2 Downshift Solenoid.

  3. With Tech 2 command the 3-2 shift solenoid ON and OFF.

Does the test lamp turn on and off with each command?

Go to Step 8

Go to Step 7

7

Is the test lamp always illuminates?

Go to Step 15

Go to Step 16

8
  1. Remove J 44152 from the harness connector X121 - X1 and install on to the transmission connector X121 - X1.
  2. Using a multimeter set to measure resistance, probe across transmission connector X121 - X1 pins E and S

Does the multimeter display 20-32  Ω?

Go to Step 9

Go to Step 10

9

Using a multimeter set to measure resistance, probe between:

    • Transmission connector X121 - X1 pin E and a known ground.
    • Transmission connector X121 - X1 pin S and a known ground.

Does the multimeter display greater than 250k Ω in both instances?

Check for an intermittent fault in the circuit, refer to Testing for Intermittent Conditions and Poor Connections

Go to Step 11

10
  1. Remove J 44152 from the transmission.
  2. Gain access to the 3-2 SS and the control valve body wiring harness, refer to Control Valve Body Disassemble.
  3. Disconnect the internal connector from the 3-2 SS.
  4. Using a multimeter set to measure resistance, probe across the 3-2 pins.

Does the multimeter display 20-32 Ω?

Replace the control valve body wiring harness, refer to Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness

Go to Step 18

Replace the 3-2 SS, refer to 2-3 Shift Solenoid Valve Replacement

Go to Step 18

11
  1. Remove J 44152 from the transmission.
  2. Gain access to the 3-2 SS and the control valve body wiring harness, refer to Control Valve Body Disassemble.
  3. Disconnect the internal connector from the 3-2 SS.
  4. Using a multimeter set to measure resistance, probe between each of the 3-2 SS pins and the transmission case.

Does the multimeter display 250k Ω in both instances?

Replace the control valve body wiring harness, refer to Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness

Go to Step 18

Replace the 3-2 shift solenoid, refer to 2-3 Shift Solenoid Valve Replacement

Go to Step 18

12

Test circuit 339 for a short to ground between connector X121 - X1 pin E and the splice.

Did you find and correct the condition?

Go to Step 18

Go to Step 13

13
  1. Gain access to the control valve body wiring harness, refer to Control Valve Body Disassemble.
  2. Test for a short to ground in the control valve body wiring harness.

Did you find a short ground condition?

Replace the control valve body wiring harness, refer to Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness

Go to Step 18

Go to Step 14

14
  1. Test each solenoid in the transmission for a short to ground, refer to Testing for Intermittent Conditions and Poor Connections.
  2. Replace the faulty solenoid as necessary.

Did you complete the replacement?

Go to Step 18

--

15

Using a multimeter, test circuit 687 for a short to ground.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

16

Using a multimeter, test circuit 687 for an open circuit.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

17

Replace the TCM, refer to Transmission Control Module Replacement.

Did you complete the replacement?

Go to Step 18

--

18

Perform the following procedure in order to verify the repair:

  1. On Tech 2 select:

    2. Diagnostic Trouble Codes / Clear Engine and Transmission DTCs.

  2. Follow the instructions on Tech 2 and clear the DTCs.
  3. On Tech 2 select:

    4. Automatic Transmission / Data Display / Transmission Data.

  4. Drive the vehicle in D3 or D4 and perform a 3-2 downshift. Ensure the 3-2 Downshift Solenoid parameter displays On when the shift occurs.
  5. On Tech select:

    6. Diagnostic Trouble Codes / Read DTC Information.

Has DTC P0787 set?

Go to Step 2

Go to Step 19

19

On Tech select:

Diagnostic Trouble Codes / Read DTC Information.

Does Tech 2 display any DTCs you have not diagnosed?

Refer to Diagnostic Trouble Code (DTC) List/Type

System OK

When all diagnosis and repairs are completed, check the system for correct operation.