GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2009 🢒 Vibe - AWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0787 or P0788

Circuit Description

Shift solenoid valve ST is switched ON/OFF by a signal from the engine control module (ECM) so that letting in or out timing of the 2nd brake is adjusted by operating orifice control valve. Therefore, shift solenoid valve ST operates when letting in or out reverse clutch.

If the shift solenoid valve ST is broken, the shift shock becomes big.

When there is an open or short circuit in any shift solenoid valve circuit, the ECM detects the problem, and illuminates the MIL and stores the DTC. The ECM performs the fail-safe and turns on the other shift solenoid valves in good condition.

DTC Descriptor

This diagnostic procedure supports the following DTC:

    • DTC P0787 Shift / Timing Solenoid Low (Shift Solenoid Valve ST)
    • DTC P0788 Shift / Timing Solenoid High (Shift Solenoid Valve ST)

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P0787

The ECM detects short in solenoid valve ST circuit two times when valve is operated.

P0788

The ECM detects an open in solenoid valve ST circuit two times when solenoid valve in not operated.

Action Taken When the DTC Sets
    • DTCs P0787 and P0788 are type C DTCs.
    • The malfunction indicator lamp (MIL) illuminates the first time the diagnostic runs with the fault active.

Conditions for Clearing the MIL/DTC

The DTC will clear when conditions for setting the DTC have been repaired.

Step

Action

Values

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

Connector End View Reference: Component Connector End Views

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. Turn the ignition to OFF.
  2. Disconnect the transmission connector B90.
  3. Measure the resistance between terminal 2 and body ground.

Is the resistance measured within specified value?

11 to 15 Ohms

Go to Step 3

Go to Step 4

3
  1. Connect the transmission connector B90.
  2. Disconnect the ECM connector C19.
  3. Measure the resistance between connector C19 terminal 80 and body ground.

Is the resistance measured within specified value?

11 to 15 Ohms

Go to Step 8

Go to Step 5

4
  1. Turn the ignition to OFF.
  2. Remove the shift solenoid valve ST.
  3. Measure the resistance between shift solenoid valve terminal and the shift solenoid body.
  4. Connect the positive lead to the terminal of the solenoid connector and the negative lead to the solenoid body, then check the movement of the valve.

Is the resistance measured within specified value and does the solenoid make an operating sound?

11 to 15 Ohms

Go to Step 6

Go to Step 7

5

Repair or replace harness or connector of the ECM. Refer to Wiring Repairs and Connector Repairs.

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Go to Step 9

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6

Repair or replace harness or connector of the shift solenoid valve ST. Refer to Wiring Repairs and Connector Repairs.

Did you complete the repair or replacement?

--

Go to Step 9

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7

Replace the shift solenoid valve ST.

Did you complete the replacement?

--

Go to Step 9

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8

Replace the ECM. Refer to Control Module References.

Did you complete the replacement?

--

Go to Step 9

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9
  1. Use the scan tool in order to clear the DTC.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK