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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 250 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING - 6.6L)FUEL SYSTEMSFUEL INJECTOR BALANCE TEST WITH TECH 2DIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. 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 CONTROL under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Are any DTCs set other than P0300, P0301-P0308? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If no, go to next step.
    3. NOTE: The balance rates may not register when engine is off idle or engine coolant temperature is less than 126°F (52°C).
  3. Start and operate engine at idle. Using scan tool, observe the Balancing Rate Cyl.1-8 parameters. Are all of the Balancing Rate parameters within -4 mm3 and +4 mm3 ? If yes, go to step  5 . If no, go to next step.
  4. Graph the Fuel Pressure Regulator. Refer to FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article. Is fuel pressure regulator graph normal? If yes, go to step  6 . If no, go to step  8 .
    5. NOTE: The fuel injector balance test must be performed under the conditions for which the concern occurred. The concern must be duplicated during the test. Do not operate cruise control during this test.
  5. Observe engine speed or other customer concern. Using scan tool, perform Cylinder Power Balance Test in Special Functions. Do any of the cylinders indicate a different engine speed change than the others, or lessen the customer's concern? If yes, go to next step. If no, system is okay.
  6. Perform engine compression test. Do any of the cylinders have low compression? If yes, diagnose engine mechanical problem. If no, go to next step.
  7. Replace faulty fuel injectors on cylinders that had poor RPM drop, high balance rates, or a noise/smoke change. See FUEL INJECTOR under FUEL SYSTEMS in REMOVAL & INSTALLATION - SIERRA & SILVERADO - DIESEL article. After replacing fuel injector(s), go to step  9 .
  8. Replace fuel pressure regulator. See FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL & INSTALLATION - SIERRA & SILVERADO - DIESEL article. After replacing fuel pressure regulator, go to next step.
  9. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 6.6L SIERRA & SILVERADO - DIESEL article.
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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.