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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 425 (ENGINE CONTROLS TROUBLESHOOTING - NO CODES - 3.8L)PRELIMINARY INSPECTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Preliminary Inspection

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Preliminary Inspection
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Pontiac Grand Prix, 2003 Pontiac Bonneville, 2003 Chevrolet Monte Carlo, 2003 Chevrolet Impala, and 2003 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: To prevent damage caused by the improper probing of connector terminals, use Connector Test Adapter Kit (J 35616-A) for any test that requires probing the PCM harness connectors, the electrical center fuse/relay cavities, component terminals or component harness connectors.
  • Verify on-vehicle diagnostics are working by performing DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article. Verify no DTCs are stored, scan tool data is within normal operating range. Verify customer complaint. Perform visual/physical check.
  • Ensure PCM grounds are clean, tight, and properly located.
  • Check vacuum hoses for splits, kinks, leaks, restrictions and proper connections. Ensure vacuum hoses are correctly routed as shown on vehicle emission control information label.
  • Check for air leaks at all intake manifold sealing surfaces.
  • Check ignition wires for cracking, hardness, proper routing and carbon tracking.
  • Check wiring for proper connections and routing, pinches, burns, cuts or other damage.
  • Ensure PCM and MIL are functioning properly.
  • Ensure there are no DTCs stored, or only intermittent DTCs are present.
  • Ensure fuel control system is operating properly. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
  • Perform fuel system pressure test. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
  • Perform a careful visual inspection of all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures will normally recommend testing of a specific system or component, such as EGR, ignition, TCC, etc. See SYSTEM & COMPONENT TESTING - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article for test procedures. If the condition cannot be duplicated, or is determined to be intermittent, see INTERMITTENTS  .

NOTE: If PCM displays data but engine fails to start, see NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
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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.