GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1996 🢒 GMC G Van 🢒 DTC 🢒 DTC P0756 2-3 (B) Shift Solenoid 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 Valve (2-3 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 Shift Solenoid Valve (1-2 SS Valve), the 2-3 SS Valve allows four different shifting combinations.

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

Conditions for Setting the DTC
    • No TP DTCs P0122 or P0123
    • No VSS Assy. DTC P0502
    • No TFT Sensor DTCs P0712 or P0713
    • No TCC Stuck ON DTC P0742
    • No 1-2 SS Valve DTC P0753
    • No 2-3 SS Valve DTC P0758
    • No TFP Val. Position Sw. DTC P1810
    • No TCC PWM Sol. Valve DTC P1860
    • No TCC Sol. Valve DTC P1864
    • No 3-2 SS Valve Assy. DTC P1886
    • The vehicle speed is greater than 24 km/h (15 mph).
    • The gear range is D4.
    • The engine speed is greater than 450 RPM for 8 seconds.
    • The transmission fluid temperature is 20-130°C (68-266°F).
    • The TCC is OFF.

All of the above conditions are met two consecutive times and either of the following two fail conditions occurs:

  1. The solenoid is stuck ON and Cases 2 and 3 occur two consecutive times.
  2. The solenoid is stuck OFF and Cases 1 and 3 occur two consecutive times.

    3. Case 1

    • The TP angle is greater than 45%.
    • First gear is commanded for 2 seconds.
    • The speed ratio is 0.5-2.6 (speed ratio is the engine speed divided by the output speed).
    • The transmission output speed is 600-1500 RPM.
    • The TCC slip speed is -100 to -3000 RPM for 1 second.

    Case 2

    • The TP angle is 13-50%.
    • The TP angle is within +/- 3%.
    • Third gear is commanded for 2 seconds.
    • The 3rd gear speed ratio is greater than the last 2nd gear speed ratio minus 0.25.
    • The 3rd gear TCC slip speed is greater than or equal to the last 2nd gear TCC slip speed plus 300 RPM for 2.5 seconds.
    • Discontinue the test if time since the shift commanded is 6 seconds.

    Case 3

    • The TP angle is greater than 13%.
    • Fourth gear is commanded for 1 second.
    • The speed ratio is 2.05-8.
    • The transmission output speed is 1400-2500 RPM.
    • The TCC slip speed is 1000-4000 RPM for 1 second.

Action Taken When the DTC Sets
    • The VCM commands maximum line pressure.
    • The VCM freezes shift adapts from being updated.
    • The VCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
    • The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
    • The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids
    • Verify that the transmission meets the specifications in the 4L60-E shift speed chart.
    • 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 scan tool commanded all shifts, that all shift solenoids responded correctly, but all the shifts did not occur.

DTC P0756 2-3 Shift Solenoid Valve (2-3 SS Valve) -- Performance

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Section 6:

Powertrain On Board Diagnostic (OBD) System Check (4.3L)

Powertrain On Board Diagnostic (OBD) System Check (5.0L and 5.7L)

2

  1. Install the scan tool (tech 1) ®.
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTCs, 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. While the engine is operating, raise the drive wheels.
  5. With the transmission in D4 range, use the scan tool to command 1st, 2nd, 3rd, and 4th gears while accelerating the vehicle.

Did you detect a 1-2-2-1 or 4-3-3-4 only shift pattern? (Road testing the vehicle may be necessary).

--

Go to Step 3

Go to Diagnostic Aids

3

Check the shift solenoid/hydraulic circuit for:

    • An internal malfunction
    • Damaged seals
    • Refer to the diagnosis charts.

Did you find and correct a problem?

--

Go to Step 4

--

4

In order to verify your repair, perform the following procedure:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions (only if traffic and road conditions permit):
    4. 3.1. Hold the throttle at 50% and accelerate to 64 km/h (40 mph).
    3.2. Stop the vehicle, engine idling.
    3.3. Hold the throttle at 25% and accelerate to 80 km/h (50 mph).
  4. Select Specific DTC. Enter DTC P0756.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1