Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 143 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING)FUEL SYSTEM (GASOLINE)FUEL INJECTOR COIL TEST (4.2L)DIAGNOSTIC PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Diagnostic Procedure
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedure
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2002 Saturn Vue, 2002 Pontiac Montana, 2002 Pontiac Aztek, 2002 Oldsmobile Silhouette, and 2002 Oldsmobile Bravada. However, it is still accessible from the selected car via links, so may be relevant.
- Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. After performing Diagnostic System Check - Engine Controls, go to next step.
- 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.
- Disconnect fuel injector multi-way harness connector. With DMM, measure resistance of each fuel injector between Ignition Feed circuit and Fuel Injector Control circuit, at multi-way connector. Do any fuel injectors display a resistance outside 11-14 ohms? If yes, go to step 6. If no, go to DIAGNOSTIC AIDS .
- Disconnect fuel injector multi-way harness connector. With DMM, 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 equal to, or less than 3 ohms? If yes, go to DIAGNOSTIC AIDS . If no, go to next step.
- Add all fuel injector resistance values, to obtain a total resistance value. Divide total resistance value by number of fuel injectors to obtain an average resistance value. Subtract lowest and highest individual fuel injector resistance values from average resistance value. Replace fuel injector that displays greatest resistance difference, more or less than average. After repairs, go to step 7.
- Replace fuel injector(s) that are outside of 11-14 ohms range. After repairs, go to next step.
- Operate system in order to verify 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.