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For 1990-2009 cars only
Makes 🢒 Holden 🢒 2005 🢒 Commodore Berlina 🢒 DTC 🢒 DTC P0788

DTC P0788 V6

DTC Description

This diagnostic procedure supports DTC P0788 3-2 Shift Solenoid (SS) Control Circuit High 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 short to voltage in the 3-2 shift solenoid valve control circuit, then DTC P0788 sets. DTC P0788 is a type A DTC.

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 450 RPM for 5 seconds.
    • The engine is not in fuel cut off.

Conditions for Setting the DTC

DTC P0788 sets if the TCM commands the solenoid on and the voltage feedback remains high, battery voltage.

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 second 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 P0788 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 tip 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 action when the ignition is off long enough in order to power down the TCM.

Test Description

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

2 Checks for a short to voltage in the 3-2 SS signal circuit.

3 Checks for the serviceability of the 3-2 SS.

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 is set. Using Tech 2 clear the DTC(s) erases the Freeze Frame/Failure Record records the TCM.

  3. On Tech 2 select: Transmission/Automatic Transmission/Diagnostic Trouble Codes/Freeze Frame.
  4. Select the relevant DTC and not the parameters at the time of the DTC setting.
  5. On Tech 2 select: Diagnostic Trouble Codes/Clear Engine & Transmission DTCs.
  6. Follow the instructions on Tech 2 and clear the DTCs.
  7. Turn off the ignition.
  8. Disconnect connector X121-X1 from the transmission.

    9. Important: Additional DTCs may set

  9. Install Tool No. J 44152 Jumper Harness (20 pins) on to the harness connector X121-X1.
  10. Turn on the ignition, with the engine off.
  11. Using a test lamp and Tool No. J 35616 , probe between connector X121-X1 pin S and a known ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 3

3
  1. Install Tool No. J 44152 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 less than 20 Ω?

Go to Step 4

Go to Step 6

4
  1. Remove Tool No. 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 SS pins.

Does the multimeter display less than 20 Ω?

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

Go to Step 7

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 7

5

Test circuit 687 for a short to voltage.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6

Replace the TCM, refer to Transmission Control Module Replacement.

Did you completer the replacement?

Go to Step 7

-

7

Perform the following procedure in order to verify the repair:

  1. On Tech 2 select: Diagnostic Trouble Codes/Clear Engine and Transmission DTCs.
  2. Follow the instructions on Tech 2 and clear any DTCs.
  3. On Tech 2 select: 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 and Off in all other instances.
  5. On Tech 2 select: Diagnostic Trouble Codes/Read DTC Information.

Has DTC P0787 set?

Go to Step 2

Go to Step 8

8

On Tech 2 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 correction operation.