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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 2 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS - 5.3L)SYSTEM TESTSMALFUNCTION INDICATOR LAMP ALWAYS ONMIL OPERATION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

MIL Operation

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION MIL Operation
WARNING: This page is about a different variant/trim than selected.

The Malfunction Indicator Lamp (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

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