GM Service Manual Online
For 1990-2009 cars only

Object Number: 1058906  Size: MF
OBD II Symbol Description Notice

Circuit Description

The torque converter has an electrically controlled capacity clutch (ECCC). At certain speeds , the TCC lockup pressure control (PC) solenoid is precisely controlled to maintain a small amount of slippage between the engine and the transaxle, reducing driveline torsional disturbances. The transmission control module (TCM) uses information from the output speed sensor (OSS) to determine if shudder is present by calculation of OSS frequency variance. The TCM monitors the OSS to detect shudder while the TCC is partially applied. If too much shudder is detected with the TCC partially applied, the TCM will then release the TCC, and monitor the OSS again for shudder. This allows the TCM to determine if the shudder is caused by the TCC system or by a rough road surface. DTC P0744 sets when the OSS indicates too much TCC shudder with the TCC partially applied, and no shudder with the TCC released. DTC P0744 is a C type DTC.

Conditions for Running the DTC

    • No TR switch DTC P0705.
    • No TFT DTCs P0711, P0712 or P0713.
    • No ISS DTC P0717.
    • No OSS DTC P0722.
    • No ratio DTC P0730.
    • No solenoid DTCs P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0983, P0985 or P0986.
    • No incorrect shifting DTC P1719.
    • No engine torque DTC P1781.

Conditions for Setting the DTC

One of the following conditions occur:

    • OSS signal cycles at 18.2-133 Hz, 8 times within 225 ms
    • OSS signal cycles at 8.3-15.6 Hz, 20 times within 930 ms

Action Taken When the DTC Sets

    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
    • 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 P0744 in TCM history.

Conditions for Clearing the MIL/DTC

    • A scan tool can clear the DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

Diagnostic Aids

The following conditions can cause DTC P0744 to set:

    • Incorrect transmission fluid level.
    • Degraded transmission fluid.
    • Incorrect transmission fluid. This DTC may set in the transmission is not filled with T-IV® automatic transmission fluid.
    • Loose or damaged OSS
    • Electromagnetic interference (EMI)
    • Shift solenoid valve 4 leaking or stuck open
    • TCC lockup pressure control (PC) solenoid stuck
    • Worn or damaged torque converter
    • A condition that causes any of the following DTCs to set:
       - DTC P0722
       - DTC P0727
       - DTC P0733
       - DTC P0966
       - DTC P0967
       - DTC P0982

Test Description

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

  1. Degraded or incorrect transmission fluid.

  2. A low transmission fluid condition may cause this DTC to set.

  3. A loose or damaged OSS can cause this DTC to set.

  4. A stuck or leaking shift solenoid valve 4 may cause this DTC to set.

  5. A stuck TCC lockup PC solenoid may cause this DTC to set.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81)

2

Inspect for correct transmission fluid level. Refer to Transmission Fluid Check .

Is the transmission fluid level correct?

--

Go to Step 3

Go to Step 4

3

Inspect the transmission fluid for the following conditions:

    • Degraded transmission fluid
    • Incorrect transmission fluid
    • Transmission oil life is less than 10%

Did you find a condition?

--

Go to Step 18

Go to Step 5

4

  1. Visually inspect the transmission and transmission cooling system for fluid leaks. Refer to Fluid Leak Diagnosis .
  2. Repair leaks as necessary.
  3. Fill the transmission to the proper fluid level.

Did you complete the action?

--

Go to Step 19

--

5

Important: If any of the following DTCs are set, they must be diagnosed before attempting to diagnose DTC P0744:

  1. DTC P0722
  2. DTC P0727
  3. DTC P0733
  4. DTC P0966
  5. DTC P0967
  6. DTC P0982

Are any of the above DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List/Type

Go to Step 6

6

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

       • Before clearing the DTC, use the scan tool in order to record the ECM and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Failure Records from the ECM and TCM.
       • Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the ECM and TCM.

  4. Record the DTC Failure Records.
  5. Clear the DTC.
  6. Use the scan tool snapshot mode in order to record the following parameters:
  7. • Commanded Gear
    • Gear Ratio
    • TCC Slip
  8. Drive the vehicle in DRIVE (D) and record the gear ratio while accelerating in 3rd gear.

Is the 3rd gear ratio equal to the specified value, and TCC slip in 3rd-5th gears?

2.89:1

Go to Intermittent Conditions in Engine Controls - 3.0L (L81)

Go to Step 7

7

  1. Drive the vehicle.
  2. Observe Transmission OSS with a scan tool.

Is Transmission OSS reading correctly?

--

Go to Step 8

Go to Step 13

8

Test for correct line pressure. Refer to Line Pressure Check .

Did you find and correct a low line pressure condition?

--

Go to Step 18

Go to Step 9

9

  1. Remove the control valve body cover (29). Refer to Control Valve Body Cover Removal .
  2. Inspect the inside of the control valve body cover (29) for excessive sediment.

Did you find excessive amounts of sediment?

--

Go to Step 17

Go to Step 10

10

Inspect the control valve body assembly (39) for the following condition:

    • Stuck open shift solenoid valve 4 assembly
    • Leaking shift solenoid valve 4 assembly

Refer to Control Valve Rear Body Disassemble and Control Valve Body Disassemble - Middle .

Did you find a condition?

--

Go to Step 14

Go to Step 11

11

Inspect the control valve body assembly (39) for a stuck TCC lockup pressure control (PC) solenoid condition.

Did you find a condition?

--

Go to Step 15

Go to Step 12

12

Inspect for a worn or damaged torque converter condition. Refer to Torque Converter Assembly Removal

Did you find a condition?

--

Go to Step 16

Go to Diagnostic Aids

13

Replace the OSS. Refer to Output Speed Sensor Replacement

Did you complete the action?

--

Go to Step 19

--

14

Replace the shift solenoid valve 4 assembly Refer to Control Valve Body Assembly Disassemble

Did you complete the action?

--

Go to Step 19

--

15

Repair or replace the valve body. Refer to Fastener Tightening Specifications

Did you complete the action?

--

Go to Step 19

--

16

Replace the torque converter assembly. Refer to Torque Converter Assembly Removal

Is the action complete?

--

Go to Step 18

--

17

Repair or replace the transmission. Refer to Transmission Replacement .

Is the action complete?

--

Go to Step 18

--

18

  1. Replace the transmission fluid. Refer to Transmission Fluid Replacement .
  2. Inspect for the correct level of transmission fluid.
  3. Add new fluid as necessary.
  4. Important: The Reset Trans Adapts function will clear all adapt cells. This may affect transmission performance. The TCM will update the adapt cell values as the vehicle is driven.

  5. Use the scan tool in order to perform the following:
  6. • Reset the transmission oil life monitor to 100 percent.
    • Reset Trans Adapts.

Did you complete the above procedures?

--

Go to Step 19

--

19

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle.
  4. Select Specific DTC.
  5. Enter DTC P0744.

Does the DTC reset?

--

Go to Step 2

Go to Step 20

20

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 in Engine Controls - 3.0L (L81)

System OK