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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 526 (CHARGING SYSTEM)ON-VEHICLE TESTINGENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECKDIAGNOSTIC PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedure

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform battery inspection test. See BATTERY TESTING & INSPECTION  under ON-VEHICLE TESTING. Go to next step.
  2. Connect scan tool to Data Link Connector (DLC). See COMPONENT LOCATIONS  . Turn ignition switch RUN position. If scan tool powers up, go to next step. If scan tool does not power up, perform appropriate test. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  3. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the Class 2 Power Mode parameter. The ignition switch parameter reading should match the ignition switch position for all switch positions. If reading is as specified, go to next step. If reading is not as specified, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  4. Turn ON the ignition, with the engine OFF. Attempt to communicate with each of the following modules on the class 2 serial data circuit:
    • Body Control Module (BCM).
    • Instrument Panel Cluster (IPC).
    • Powertrain Control Module (PCM).
    The scan tool should communicate with all modules on the class 2 serial data circuit. If communication is as specified, go to next step. If communication is as not specified, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  5. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and module that set DTC. If DTCs are displayed, go to next step. If no DTCs are displayed, repair charging system by symptom. See SYMPTOM INDEX  table under SYSTEM TESTS.
  6. If scan tool displays DTCs which begin with "U", perform appropriate test in accordance with DTC retrieved. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display DTCs which begin with "U", go to next step.
  7. If scan tool does not display any DTCs which begin with "P", go to next step. If scan tool displays any DTCs which begin with "P", perform appropriate test in accordance with DTC retrieved. See SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  8. If scan tool displays DTCs which begin with "B", perform appropriate test in accordance with DTC retrieved. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display DTCs which begin with "B", perform appropriate test in accordance with DTCs retrieved. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
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.