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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1049 (Automatic Transmission - ALLISON - DTC P0218 To DTC P0732) >> DTC P0634 >> Diagnostic Aids

Diagnostic Aids

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Clean the TCM if necessary. Excessive road debris will reduce the effectiveness of the heat sink on the TCM and could cause the internal temperature to rise.

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. 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 for reference. The Clear Info function will erase the data.
  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Using the scan tool, drive the vehicle and monitor TCM internal temperature.
Did DTC P0634 return?		 Go to Step 3  Go to Diagnostic Aids
3
  1. Inspect the TCM and surrounding area for obstructions.
  2. Ensure the engine cooling fan is operating properly.
Do you find and correct the condition?		 Go to Step 5  Go to Step 4 
4
IMPORTANT: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.
Replace the TCM. Refer to Control Module References for replacement, setup, and programming.Did you complete the replacement?		 Go to Step 6  -
5 Perform the following procedure in order to verify the repair:
  1. Clear the DTC.
  2. Start the engine.
  3. Using the scan tool, drive the vehicle and monitor TCM internal temperature.
  4. Select Specific DTC.
  5. Enter DTC P0634.

Has the test run and passed?		 Go to Step 6  Go to Step 2 
6 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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