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Diagnostic Procedures

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Suburban, and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. After performing diagnostic system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command fuel pump relay on and off. Repeat commands as necessary. Does fuel pump turn on and off? If yes, problem is intermittent. See DIAGNOSTIC AIDS  . If no, go to next step.
  3. Using scan tool, command fuel pump relay on and off. Fuel pump relay is located in underhood fuse/relay block. See Figure . Do you hear a click when you command fuel pump relay on and off? If yes, go to step  9 . If no, go to next step.
  4. Turn ignition off. Remove fuel pump relay. Turn ignition on, with engine off. Probe control circuit of fuel pump relay with a test light that is connected to a good ground. See Figure . Command fuel pump relay ON and OFF with a scan tool. Does test light turn ON and OFF? If yes, go to next step. If no, go to step  6 .
  5. Connect a test light between control circuit of fuel pump relay and ground circuit of fuel pump relay. Command fuel pump relay on and off with a scan tool. Does test light turn on and off? If yes, go to step  19 . If no, go to step  21 .
  6. Does test light remain illuminated with each command? If yes, go to next step. If no, go to step  8 .
  7. Test control circuit of fuel pump relay for a short to voltage. See Figure . Did you find and correct condition? If yes, go to step  27 . If no, go to step  26 .
  8. Test control circuit of fuel pump relay for a short to ground or an open. Did you find and correct condition? If yes, go to step  27 . If no, go to step  19 .
  9. Turn ignition on, with engine off. Does fuel pump operate continuously? If yes, go to next step. If no, go to step  11 .
  10. Turn ignition off. Remove fuel pump relay. Turn ignition on, with engine off. Does fuel pump operate continuously? If yes, go to step  21 . If no, go to step  25 .
  11. Inspect fuel pump fuse. Is fuse open? If yes, go to next step. If no, go to step  14 .
  12. Test supply voltage circuit of fuel pump for a short to ground between fuel pump fuse and fuel pump. Replace fuel pump fuse, if necessary. Did you find and correct condition? If yes, go to step  27 . If no, go to next step.
  13. Connect all disconnected electrical components. Install a new fuel pump fuse. Command fuel pump relay on with a scan tool. Inspect fuel pump fuse. Is fuse open? If yes, go to step  24 . If no, problem is intermittent.
  14. Turn ignition off. Remove fuel pump relay. Turn ignition on, with engine off. Probe ignition 1 voltage circuit of fuel pump relay, switch side, with a test light connected to a good ground. Does test light illuminate? If yes, go to next step. If no, go to step  23 .
  15. Connect a 20-amp fused jumper wire between ignition 1 voltage circuit of fuel pump relay and supply voltage circuit of fuel pump. Does fuel pump operate? If yes, go to step  19 . If no, go to next step.
  16. Test supply voltage circuit of fuel pump for an open or high resistance between fuel pump relay and fuel pump. Did you find and correct condition? If yes, go to step  27 . If no, go to next step.
  17. Test ground circuit of fuel pump for an open or high resistance. Did you find and correct condition? If yes, go to step  27 . If no, go to next step.
  18. Inspect for poor connections at the fuel pump. Did you find and correct the condition? If yes, go to step  27 . If no, go to step  24 .
  19. Test for poor connection at fuel pump relay. Did you find and correct condition? If yes, go to step  27 . If no, go to step  25 .
  20. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  27 . If no, go to step  26 .
  21. Repair the supply voltage circuit of the fuel pump for a short to voltage. After repairs, go to step  27 .
  22. Repair open in fuel pump relay ground circuit. After repairs, go to step  27 .
  23. Repair the battery voltage circuit of the fuel pump relay switch. After repairs, go to step  27 .
  24. Replace fuel pump. After replacing fuel pump, go to step  27 .
  25. Replace fuel pump relay. After replacing relay, go to step  27 .
  26. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram ECM. After replacing PCM, go to next step.
  27. Operate system in order to verify repair. Did you correct condition? If yes, system is okay. If no, go to step  2 .
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