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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Savana 🢒 DTC 🢒 DTC P0756 2-3 Shift Solenoid Valve Performance

Object Number: 42270 Size: MF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The 2-3 shift solenoid (SS) valve controls the fluid flow acting on the 2-3 shift valves. The solenoid is a normally-open exhaust valve. With the 1-2 SS valve, the 2-3 SS valve allows four different shifting combinations.

When the VCM detects a 1-2-2-1 or a 4-3-3-4 shift pattern, depending on the state of the mechanical failure, then DTC P0756 sets. DTC P0756 is a type A DTC.

Conditions for Running the DTC
    • No TP sensor DTCs P0122 or P0123.
    • No VSS assembly DTCs P0502 or P0503.
    • No TFT sensor DTCs P0711, P0712 or P0713.
    • No TCC solenoid valve DTC P0740.
    • No TCC stuck ON DTC P0742.
    • No 1-2 SS valve DTC P0753.
    • No 2-3 SS valve DTC P0758.
    • No 3-2 SS valve assembly DTC P0785.
    • No TFP manual valve position switch DTC P1810.
    • No TCC PWM solenoid valve DTC P1860.
    • The vehicle speed is greater than 8 km/h (5 mph).
    • The gear range is D4.
    • The TP angle is 15-50%.
    • The TP angle is constant within +/- 7%.
    • The VCM commands a 1-2, 2-3 and 3-4 shift.
    • The engine vacuum is 0-105 kPa.
    • The engine torque is 5-450 lb ft.
    • The engine speed is greater than 450 RPM for 5 seconds.
    • The engine is not in fuel cutoff.
    • The transmission fluid temperature is 20-130°C (68-266°F).

Conditions for Setting the DTC

DTC P0756 sets if the following conditions occur three times:

    • Third gear is commanded for 2 to 5 seconds.
    • The speed ratio in 3rd gear does not drop more than 0.3 from the last speed ratio in 2nd gear (speed ratio is engine speed divided by transmission output speed).
    • The TCC slip speed in 3rd gear remains 300 RPM higher than the last TCC slip speed in 2nd gear.

All of the above conditions are met for 1.5 seconds and one of the following conditions occurs:

Condition 1

    • First gear is commanded for 2 seconds.
    • The transmission output speed is 400-1500 RPM.
    • The speed ratio is 0.5 to 3.0.
    • The TCC slip speed is -3000 to -100 RPM for 1 second.

Condition 2

    • Fourth gear is commanded for 1 second.
    • The transmission output speed is 1400-2500 RPM.
    • The speed ratio is 2.05 to 0.8.
    • The TCC slip speed is 1000 to 4000 RPM for 1 second.

Action Taken When the DTC Sets
    • The VCM illuminates the malfunction indicator lamp (MIL).
    • The VCM commands third gear only.
    • The VCM inhibits TCC engagement.
    • The VCM commands maximum line pressure.
    • The VCM freezes shift adapts from being updated.
    • The VCM stores DTC P0756 in VCM history.

Conditions for Clearing the MIL/DTC
    • The VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
    • A scan tool clears the DTC from VCM history.
    • The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
    • The VCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the VCM.

Diagnostic Aids
    • Verify that the transmission meets the specifications in the Shift Speed table.
    • Other internal transmission failures may cause more than one shift to occur.
    • Refer to the Shift Solenoid Valve State and Gear Ratio table.

Test Description

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

  1. This step verifies that the VCM commanded all shifts, that all shift solenoids responded correctly, but all the shifts did not occur.

DTC P0756 2-3 Shift Solenoid Valve -- Performance

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check (4.3L) or Powertrain On Board Diagnostic (OBD) System Check (5.0L and 5.7L) in Engine Controls

2
  1. Install the Scan Tool .
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the VCM.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Drive the vehicle in D4 range, under the following conditions:

    6. Accelerate the vehicle, ensuring that the VCM commands 1st, 2nd, 3rd, and 4th gears.

Did you detect a 1-2-2-1 or 4-3-3-4 shift pattern?

--

Go to Step 3

Go to Diagnostic Aids

3

Inspect the shift solenoid/hydraulic circuit for the following conditions:

    • An internal malfunction
    • Damaged seals on the shift solenoid valves.
        Refer to Shift Solenoid Leak Test .

Did you find and correct the condition?

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Go to Step 4

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4

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Drive the vehicle in D4 under the following conditions (only if traffic and road conditions permit):
    4. • Hold the throttle at 50% and accelerate to 64 km/h (40 mph).
    • Stop the vehicle, engine idling.
    • Hold the throttle at 25% and accelerate to 80 km/h (50 mph).
  4. Select Specific DTC.
  5. Enter DTC P0756.

Has the test run and passed?

--

System OK

Go to Step 1