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Diagnostic Procedures

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Sonoma, 2003 GMC Safari, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. 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 - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP 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 48-54 psi (334-375 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP 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 - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. If no, go to next step.
    6. CAUTION: DO NOT repeat any portion of this test before running engine in order to prevent engine from flooding.
    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. Disconnect multi-way harness connector of fuel injectors. Connect Fuel Injector Tester (J-39021) to ignition 1 voltage circuit terminal and appropriate fuel injector control circuit terminal using Connector Test Adapter Kit (J-35616-A). 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 - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  7. Replace affected fuel injectors. After repairs, go to next step.
  8. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
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