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Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel System (Gasoline) >> Fuel Pump Relay (5.0L & 5.7L) >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 5.0L & 5.7L CHEVY EXPRESS & SAVANA article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Turn ON the ignition, with the engine OFF. Command fuel pump relay ON and OFF with scan tool. Does fuel pump relay click when commanded with scan tool? If yes, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - TRUCKS article. If no, go to next step.
  3. Command fuel pump relay ON and OFF with scan tool. 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 OFF the ignition. Disconnect fuel pump relay. Turn ON the ignition, with the engine OFF. Probe Control circuit of fuel pump relay with test light that is connected to a good ground. Command fuel pump relay ON and OFF with scan tool. Does test light turn ON and OFF when commanded with scan tool? If yes, go to next step. If no, go to step  6.
  5. Connect test light between Control circuit of fuel pump relay and ground circuit of fuel pump relay. Command fuel pump relay ON and OFF with scan tool. Does test light turn ON and OFF when commanded with scan tool? If yes, go to step  19. If no, go to step  21.
  6. Does test light remain illuminated? 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. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
  8. Test Control circuit of fuel pump relay for a short to ground or an open. Did you find and correct the condition? If yes, go to step  25. If no, go to step  20.
  9. Turn ON the ignition, with the engine OFF. Does fuel pump operate continuously? If yes, go to next step. If no, go to step  11.
  10. Test supply voltage circuit of fuel pump for a short to voltage. Did you find and correct the condition? If yes, go to step  25. If no, go to step  23
  11. Inspect fuel pump fuse. Is fuel pump fuse open? If yes, go to next step. If no, go to step  14.
  12. Test supply voltage circuit of fuel pump between fuel pump fuse and fuel pump for a short to ground. Replace fuel pump fuse. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  13. Install all disconnected electrical components. Install a new fuel pump fuse, if necessary. Turn ON fuel pump with scan tool. Inspect fuel pump fuse. Is fuel pump fuse open? If yes, go to step  22. If no, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  14. Test battery voltage circuit of fuel pump relay switch for an open. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  15. Connect a 20-amp fused jumper wire between battery voltage circuit of pump relay switch 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 between fuel pump relay and fuel pump for an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
    17. NOTE: Inspect ground circuit for being tight, corrosion on terminals, or damage to wiring harness.
  17. Test ground circuit of fuel pump for an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  18. Inspect for poor connections at fuel pump. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  19. Inspect for poor connections at fuel pump relay. Did you find and correct the condition? If yes, go to step  25. If no, go to step  23.
  20. Inspect for poor connections at harness connector of PCM. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
  21. Repair open fuel pump relay ground circuit. After repairs, go to step  25.
    22. NOTE: Inspect for poor connections at fuel pump, within fuel tank, before replacing fuel pump.
  22. Replace fuel pump. Replace fuel pump fuse if necessary. After repairs, go to step  25.
  23. Replace fuel pump relay. After repairs, go to step  25.
  24. Replace PCM. Perform PCM relearn procedures. See PROGRAMMING in SELF-DIAGNOSTICS - 5.0L & 5.7L CHEVY EXPRESS & SAVANA article. After repairs, go to next step.
  25. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to step  2.
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