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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 32 (AUTOMATIC TRANSMISSION - ALLISON - DIAGNOSTICS (DTCs P0732-P0877)) >> DTC P0742 >> Test Description

Test Description

WARNING: This page is about a different variant/trim than selected.

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

  1. 2:  This step tests for TCC application at startup, stuck on.
  2. 3:  This step inspects for internal damage.
  3. 4:  This step inspects for 3 possible causes for the TCC being stuck on.
DTC P0742

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/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 (With 6.6L Engine) or Transmission Replacement (With 8.1L (L18) Engine) .
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
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