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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 35 (ENGINE CONTROL SYSTEM - SYSTEM & COMPONENT TESTING)FUEL SYSTEMSFUEL PUMP ELECTRICAL CIRCUIT DIAGNOSISDIAGNOSTIC PROCEDURE
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2

Diagnostic Procedure

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 1.8L VIBE article.
  2. Connect scan tool. Remove the bottom cushion of rear seat to gain access to the fuel sender assembly access panel. Place a listening device against the fuel sender assembly access panel. Turn ignition switch to RUN position, engine OFF. Command the fuel pump ON and OFF using the scan tool. Listen for audible fuel pump operation. Does the fuel pump operate as commanded? If yes, go to next step. If no, go to step  4 .
  3. The fuel pump electrical circuit is OK. Do you want to inspect the fuel system for the correct operating pressure? If yes, go to FUEL SYSTEM DIAGNOSIS 
  4. Is the fuel pump operating continuously when the ignition is in RUN position with engine OFF? If yes, go to step  15 . If no, go to next step.
  5. Turn the fuel pump ON and OFF while listening carefully for the operation of the circuit opening relay near the instrument panel fuse block. Did you hear the circuit opening relay click when commanded ON and OFF using the scan tool? If yes, go to step  10 . If no, go to next step.
  6. Turn ignition switch to OFF position. Remove the circuit opening relay. Turn ignition switch to RUN position, engine OFF. Probe the circuit opening relay cavity No. 1 and cavity No. 2 using a test light connected to ground. See Figure . Did the test light illuminate at both cavities? If yes, go to next step. If no, go to step  9 .
  7. Using a test light connected to battery voltage, probe the circuit opening relay control circuit cavity No. 3. Command the fuel pump ON using the scan tool. Does the test light illuminate? If yes, go to step  19 . If no, go to next step.
  8. Check for an open in the circuit opening relay control circuit. Repair as necessary. Was a wiring fault found and repaired? If yes, go to step  22 . If no, go to step  21 .
  9. Check for the cause of no ignition positive voltage to the circuit opening relay. Repair as necessary. After repair, go to step  22 .
  10. Remove the fuel sender assembly access panel. Disconnect fuel sender assembly harness connector. Probe the fuel pump ignition positive voltage circuit, terminal No. 4, using a test light connected to ground. Command the fuel pump ON using the scan tool. Does the test light illuminate? If yes, go to next step. If no, go to step  13 .
  11. Connect the test light between the fuel pump ground circuit and battery voltage. Does the test light illuminate? If yes, go to step  14 . If no, go to next step.
  12. Repair the open fuel pump ground circuit. After repair, go to step  22 .
  13. Repair open fuel pump power circuit between the circuit opening relay and fuel sender assembly. After repair, go to step  22 .
  14. Inspect the fuel sender assembly for an open or high resistance in the fuel pump positive voltage circuit and the fuel pump ground circuit. Repair or replace the fuel sender assembly as necessary. Was a repair or replacement necessary? If yes, go to step  22 . If no, go to step  20 .
  15. Remove the circuit opening relay. Is the fuel pump still operating? If yes, go to next step. If no, go to step  17 .
  16. Repair the short to voltage in the fuel pump supply circuit. After repair, go to step  22 .
  17. Turn ignition switch to OFF position. Probe the control circuit, relay socket cavity No. 3, using a test light connected to battery voltage. See Figure . Command the circuit opening relay ON and OFF with the scan tool. Did the test light stay illuminated even when the relay was commanded OFF? If yes, go to next step. If no, go to step  19 .
  18. Inspect for a short to ground in the circuit opening relay control circuit between the relay and PCM. Repair the wiring as necessary. Did you find and repair a wiring short? If yes, go to step  22 . If no, go to step  21 .
  19. Replace the circuit opening relay. After repair, go to step  22 .
  20. Replace the fuel pump. See FUEL PUMP under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. After repair, go to step  22 .
  21. Replace the PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - 1.8L VIBE article. After repair, go to step  22 .
  22. Operate vehicle within the conditions under which the original symptom was noted. Does the system operate correctly now? If yes, system is okay at this time. If no, go to DIAGNOSTIC AIDS  .
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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.