GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Avalanche - 2WD 🢒 DTC 🢒 DTC P0756

Object Number: 42270 Size: MF
Master Electrical Component List
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 2-3 SS valve is a normally-open exhaust valve that is used with the 1-2 SS valve, in order to allow 4 different shifting combinations.

When the transmission control module (TCM) detects a 4-3-3-4 shift pattern, then DTC P0756 sets. DTC P0756 is a type A DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0756 2-3 Shift Solenoid Valve Performance - No First or Second Gear

Conditions for Running the DTC
    • No input speed sensor (ISS) DTCs P0716 or P0717.
    • No output (shaft) speed sensor (OSS) DTCs P0722 or P0723.
    • No torque converter clutch (TCC) DTC P0742 or P0894.
    • No shift solenoid electrical DTCs P0973, P0974, P0976, or P0977.
    • The engine torque is greater than 50 N·m (37 lb ft).
    • The engine run time is greater than 5 seconds.
    • The transmission fluid temperature is 20-130°C (68-266°F).
    • The throttle position is 8 percent or greater.
    • The output shaft speed is 150 RPM or greater.

Conditions for Setting the DTC

Either of the following conditions must occur twice during the same trip:

    • Fail Case 1: The TCM commands 1st gear and the resulting gear ratio is 0.65:1-0.725:1 for 2 seconds.
    • Fail Case 2: The TCM commands 2nd gear and the resulting gear ratio is 0.95:1-1.05:1 for 3 seconds.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The TCM inhibits 1st gear.
    • 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 P0756 in TCM history.

Conditions for Clearing the DTC
    • The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • A scan tool 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 default actions when the ignition is OFF long enough in order to power down the TCM.

Diagnostic Aids
    • If you clear DTC P0756, and then cannot reset DTC P0756, the following conditions may exist:
       - Fluid contamination
       - Plugged fluid circuits
       - Restricted fluid circuits
    • Refer to Shift Solenoid Valve State and Gear Ratio .

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests that the TCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.

DTC P0756

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    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 TCM.

  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 TCM commands 1st, 2nd, 3rd, and 4th gears.

Did you detect a 4-3-3-4 shift pattern?

Go to Step 3

Go to Diagnostic Aids

3
  1. Inspect the shift solenoid/hydraulic circuit for the following conditions:
    2. • Debris or chips in the AFL oil passage
    • Debris or chips restricting oil flow in passage #29 of the case or through the spacer plate gasket into the valve body
    • A cracked 2-3 shift solenoid
    • A 2-3 shift valve which is stuck or hung up in the valve body bore
    • A 2-3 shuttle valve which is stuck or hung up in its bore
    • Damaged seals on the shift solenoid valves
    • Refer to Shift Solenoid Leak Test .
  2. Clean and inspect the related valves, bores and the valve body for debris or contamination.

Did you find and correct the condition?

Go to Step 4

--

4

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Drive the vehicle in D4 range under the following conditions, only if traffic and road conditions permit:

    4. Hold the throttle at 40 percent and accelerate to 64 km/h (40 mph).

  4. Select Specific DTC.
  5. Enter DTC P0756.

Has the test run and passed?

Go to Step 5

Go to Step 2

5

With the scan tool, observe the stored information, capture info, and DTC Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK