GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Silverado - 4WD 🢒 DTC 🢒 DTC P0742

Circuit Description

The transmission control module (TCM) uses data from the engine speed sensor and the turbine speed sensor to calculate the torque converter slip value. The TCM then compares this calculated slip value to a preset value in the TCM calibration.

DTC P0742 is a type B DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0742 Torque Converter Clutch (TCC) System - Stuck On

Conditions for Running the DTC
    • DTC P0122, P0123, P0716, P0717, P0721, P0722, P0743 are not active.
    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
    • The transmission must be in a forward range.
    • The torque converter clutch (TCC) is not enabled or requested.

Conditions for Setting the DTC

DTC P0742 sets when the TCM detects TCC slip speed values indicating a stuck on or locked condition for 2.5 seconds.

Action Taken When the DTC Sets
    • The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • If failure occurs before shifting is completed, the transmission will shift to NEUTRAL. If failure occurs while shifting is being completed, the transmission will shift to NEUTRAL or 1st range while diagnostic response is active.
    • If the shift selector is moved to NEUTRAL, the transmission will shift to NEUTRAL.
    • If the shift selector is moved to REVERSE, the transmission will shift to NEUTRAL or REVERSE.
    • If the shift selector is returned to DRIVE, the transmission will shift to NEUTRAL or 1st range.
    • DTC P0742 is stored in TCM history.
    • The TCM inhibits TCC engagement.
    • The TCM freezes shift adapts.

Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
    • Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
       - A bent terminal
       - A backed-out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • You may have to drive the vehicle in order to experience a condition.

Test Description

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

  1. This step tests for TCC application at startup, stuck on.

    2.

  2. This step inspects for internal damage.

    3.

  3. This step inspects for 3 possible causes for the TCC being stuck on.

Step

Action

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install the scan tool.
  2. Set the parking brake and block the wheels to prevent vehicle movement.

    3. Important: Before clearing the DTC, 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 Failures Records.
  4. Clear the DTC.
  5. Start the engine.
  6. Apply the vehicle brakes and select DRIVE.

Did the engine stall?

Go to Step 3

Go to Diagnostic Aids

3

  1. Remove the transmission oil pan. Refer to Automatic Transmission Fluid and Filter Replacement .
  2. Inspect for contaminated fluid and/or excessive material in the pan.

Is the fluid contaminated or excessive material found in the pan?

Go to Step 5

Go to Step 4

4

This condition indicates the TCC is mechanically stuck ON. Inspect for the following conditions:

  1. Faulty TCC solenoid
  2. Stuck or sticking TCC valve
  3. Restricted transmission cooler lines

Did you find and repair a condition?

Go to Step 6

--

5

Remove the transmission for overhaul or replacement. Refer to Transmission Replacement .

Did you complete the repair or replacement?

Go to Step 6

--

6

Preform the following procedure in order to verify the repair:

  1. Clear the DTC.
  2. Drive the vehicle under normal operating conditions.
  3. Using the scan tool, monitor TCC slip speed. The TCC must engage/disengage when commanded.
  4. Select Specific DTC.
  5. Enter DTC P0742.

Has the test run and passed?

Go to Step 7

Go to Step 2

7

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