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Makes 🢒 Isuzu 🢒 2006 🢒 Ascender - 2WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L60-E/4L65-E/4L70-E 🢒 DTC P0756

DTC P0756 4.2L


Object Number: 42270 Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics (4.2L)
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 powertrain control module (PCM) 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 TP sensor DTCs P0122 or P0123.
    • No VSS DTCs P0502 or P0503.
    • 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 P2761.
    • The engine speed is greater than 450 RPM for 5 seconds.
    • The engine is not in fuel cutoff.
    • The gear range is D4.
    • The TP angle is 10 percent or greater.
    • The transmission fluid temperature is 20-130°C (68-266°F).
    • The system voltage is 10-18 volts.
    • The engine torque is 68-542 N·m (50-400 lb ft).
    • The transmission output speed is 150 RPM or greater.

Conditions for Setting the DTC

DTC P0756 sets if both of the following conditions occur:

Condition 1

    • The PCM commands first gear for 2 seconds.
    • The estimated gear ratio is 0 to 1.4.
    • All conditions are met for 1 second.

Condition 2

    • The PCM commands second gear for 1 second.
    • The torque converter efficiency is greater than or equal to 0.5.
    • The estimated gear ratio is 0.9-1.2.
    • All conditions are met for 2 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL).
    • The PCM commands third gear only.
    • The PCM commands maximum line pressure.
    • The PCM inhibits TCC engagement.
    • The PCM freezes transmission adaptive functions.
    • The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
    • The PCM stores DTC P0756 in PCM history.

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

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 tests that the PCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.

DTC P0756 (4.2L)

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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 powertrain control module (PCM).

  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 PCM 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 in Vehicle DTC Information

System OK

DTC P0756 5.3L and 6.0L


Object Number: 42270 Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics (5.3L/6.0L)
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 10 percent or greater.
    • The output shaft speed is 150 RPM or greater.

Conditions for Setting the DTC

Both 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 0.69:1-1.14:1 for 1 second.
    • Fail Case 2: The TCM commands 2nd gear and the resulting gear ratio is 0.698:1-1.2:1 for 2 seconds.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
    • The TCM commands a soft landing to 2nd gear.
    • 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 transmission control module (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