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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 243 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING)FUEL SYSTEMSFUEL INJECTOR BALANCE TEST WITH SPECIAL TOOLDIAGNOSTIC 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. Perform FUEL INJECTOR COIL TEST  . After performing Fuel Injector Coil Test, go to next step.
    3. NOTE: DO NOT perform this test if ECT is greater than 201°F (94°C).
  3. Observe ECT parameter with scan tool. Does scan tool indicate ECT parameter is less than 201°F (94°C)? If yes, go to next step. If no, allow engine to cool before proceeding.
    4. NOTE: Verify there is adequate fuel in fuel tank before proceeding with this step. Fuel pump may need to be commanded ON a few times, in order to obtain highest possible fuel pressure reading. DO NOT allow engine to start.
  4. Turn ignition off. Turn off all accessories. Install fuel pressure gauge. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Observe fuel pressure gauge, with fuel pump commanded ON. Is fuel pressure within 52-59 psi (358-405 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L AZTEK & RENDEZVOUS article.
    5. NOTE: Fuel pressure may vary slightly when fuel pump stops operating. After fuel pump stops operating, fuel pressure should stabilize and remain constant.
  5. Monitor fuel pressure gauge for one minute. Does fuel pressure decrease by more than 5 psi (34 kPa)? If yes, go to FUEL SYSTEM PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L AZTEK & RENDEZVOUS article. If no, go to next step.
    6. NOTE: Fuel pressure may rise after fuel injector stops pulsing. Record fuel pressure value immediately after fuel injector stops pulsing. DO NOT record higher fuel pressure value.
  6. Connect Fuel Injector Coil/Balance Tester (J-39021), Injector Test Adapter Box (J-39021-210), and Fuel Injector Test Harness (J-39021-410) to fuel injector multi-way connector. Set amperage supply selector switch on fuel injector tester to Balance Test .5-2.5-amp position. Command fuel pump ON and then OFF with scan tool. Record fuel pressure indicated by fuel pressure gauge after fuel pressure stabilizes. This is first pressure reading. Energize fuel injector by depressing "Push to Start Test" button on fuel injector tester. Record fuel pressure indicated by fuel pressure gauge after fuel injector has stopped pulsing. This is second pressure reading. Repeat this step for each fuel injector. Subtract second pressure reading from first pressure reading for one fuel injector. Result is pressure drop value. See Figure . Obtain a pressure drop value for each fuel injector. Add all individual pressure drop values. This is total pressure drop. Divide total pressure drop by number of fuel injectors. This is average pressure drop. Does any fuel injector have a pressure drop value more than average pressure drop or less than average pressure drop by 1.5 psi (10 kPa)? If yes, go to next step. If no, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 3.4L AZTEK & RENDEZVOUS article.
  7. Replace affected fuel injectors. After repairs, go to next step.
  8. Operate system in order to verify repair. Does a driveability condition still exist? If yes, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 3.4L AZTEK & RENDEZVOUS article. If no, system is okay.
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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.