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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 975 (ENGINE CONTROLS - 4.3L (INTRODUCTION))REPAIR INSTRUCTIONSPOWERTRAIN CONTROL MODULE (PCM) REPLACEMENTREMOVAL PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Removal Procedure

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Removal Procedure
WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
  • To prevent internal PCM damage, the ignition switch must be OFF when disconnecting or connecting power to the PCM.
  • Remove any debris from around the PCM connector surfaces before servicing the PCM. Inspect the PCM module connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion onto the PCM.
  • The replacement PCM must be reprogrammed.
    IMPORTANT: It is necessary to record the remaining engine oil life. If the replacement module is not programed with the remaining engine oil life, the engine oil life will default to 100%. If the replacement module is not programmed with the remaining engine oil life, the engine oil will need to be changed at 5000 km (3,000 mi) from the last engine oil change.
  1. Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure (Single Battery) or Battery Negative Cable Disconnect/Connect Procedure (Auxiliary Battery) in Engine Electrical.
  3. Release the PCM cover mounting tabs.
  4. Release the PCM cover from the mounting brackets.
  5. Remove the PCM cover.
    6. Fig 1: View Of PCM Cover & Mounting Bracket
    GM814118Courtesy of GENERAL MOTORS CORP.
  6. Loosen the PCM electrical connector bolts (2).
    NOTE: Refer to PCM and ESD Notice in Cautions and Notices.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.