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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 243 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING)FUEL SYSTEMSFUEL INJECTOR COIL TESTDIAGNOSTIC 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 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Observe Engine Coolant Temperature (ECT) parameter with scan tool. Is ECT value within 50-90°F (10-32°C)? If yes, go to next step. If no, go to step  4 .
  3. Disconnect fuel injector multi-way harness connector. With DVOM, measure resistance of each fuel injector between Ignition Feed circuit and Fuel Injector Control circuit, at multi-way connector. See WIRING DIAGRAMS  . Do any fuel injectors display a resistance outside 11-14 ohms? If yes, go to step  5 . If no, go to DIAGNOSTIC AIDS  .
  4. Disconnect fuel injector multi-way harness connector. With DVOM, measure resistance of each fuel injector between Ignition Feed circuit and Fuel Injector Control circuit, at multi-way connector. Record each fuel injector value. Subtract lowest resistance value from highest resistance value. Is difference 3 ohms or less? If yes, go to FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL  or FUEL INJECTOR BALANCE TEST WITH TECH 2  . If no, go to step  8 .
  5. Remove upper intake manifold. After removing upper intake manifold, go to next step.
  6. Using a DVOM, measure resistance of the ignition 1 voltage circuit between the multi-way connector and affected fuel injector connector. Is resistance more than 5 ohms? If yes, go to next step. If no, go to step  9 .
  7. Repair open or high resistance in the ignition 1 voltage circuit. After repairs, go to step  11 .
  8. Add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest and the highest individual fuel injector resistance values from the average resistance value. Replace fuel injector that displays the greatest resistance difference, above or below the average. After replacing injector(s), go to step  11 .
  9. Test for an intermittent and for a poor connection at the affected fuel injector. Did you find and correct the condition? If yes, go to step  11 . If no, go to next step.
  10. Replace any fuel injectors that are out of the specified range of 11-14 ohms. After replacing injector(s), go to next step.
  11. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step  2 .
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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.