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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS - 4.2LSYSTEM TESTSMALFUNCTION INDICATOR LIGHT INOPERATIVEMIL OPERATION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

MIL Operation

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION MIL Operation

Malfunction Indicator Light (MIL) is located on the instrument panel.

MIL Function

  • The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
  • The MIL illuminates during a bulb test and a system test.
  • A Diagnostic Trouble Code (DTC) will be stored if a MIL is requested by the diagnostic.

MIL Illumination

  • MIL will illuminate with ignition ON and engine not running.
  • MIL will turn OFF when engine is started.
  • MIL will remain ON if the self-diagnostic system has detected a malfunction.
  • MIL may turn OFF if the malfunction is not present.
  • If MIL is illuminated and then engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
  • If MIL is not illuminated and engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.

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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.