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Home >> Cadillac >> 2003 >> CTS Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Fuel Systems >> Fuel Pump Electrical Circuit Diagnosis >> Diagnostic Procedure
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Diagnostic Procedure

  1. If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article.
  2. Connect scan tool. Turn ignition ON, with the engine OFF. Using a scan tool, command fuel pump relay ON and OFF. If fuel pump turns ON and OFF, check for intermittent problem. See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article. If fuel pump does not turn ON and OFF, go to next step.
  3. Remove rear seat cushion and locate fuel pump relay in right rear fuse block. See Fig 1. Command the fuel pump relay ON and OFF using a scan tool. An audible click should be heard. Do you hear a click when you command the fuel pump relay ON and OFF? If fuel pump relay clicks, go to next step. If relay does not click, go to step  9.
  4. Turn ignition ON, with engine OFF. Does fuel pump operate continuously? If fuel pump operates continuously, go to next step. If fuel pump does not operate continuously, go to step  6.
  5. Turn ignition OFF. Disconnect fuel pump relay. Turn ignition ON, with engine OFF. Does the fuel pump operate continuously? If fuel pump operates continuously, go to step  20. If fuel pump does not operate continuously, go to step  24.
  6. Is the fuel pump fuse open? If the fuel pump fuse is open, go to next step. If fuel pump fuse is okay, go to step  10.
  7. Disconnect fuel pump harness in-line connector located near the fuel tank. Test the vehicle side of the harness, for a short to ground in the fuel pump supply voltage circuit. See Fig 2. Did you find and repair a short to ground in the fuel pump supply circuit? If yes, replace fuel pump fuse and go to step  26. If no, go to next step.
  8. Lower the fuel tank if necessary. Test and/or inspect the fuel tank electrical harness for damage or a grounded fuel pump voltage supply circuit. Did you find and repair any damage or a short to ground in the fuel pump supply circuit? If yes, replace fuel pump fuse and go to step  26. If no, go to step  17.
  9. Turn ignition OFF. Disconnect fuel pump relay. Turn ignition ON, with engine OFF. Probe the fuel pump relay control circuit with a test light connected to a good ground. Command the fuel pump ON and OFF using a scan tool. If test light illuminates go to step  18. If test light does not illuminate, go to step  19.
  10. Turn ignition OFF. Disconnect fuel pump relay. Turn ignition ON, with engine OFF. Probe the fuel pump relay battery positive voltage circuit of the with a test light connected to a good ground. If the test light illuminates go to step  12. If test light does not illuminate, go to next step.
  11. Turn ignition OFF. Disconnect fuel pump fuse. Turn ignition ON, with engine OFF. Check battery positive side of the fuel pump fuse with a test light connected to a good ground. If test light illuminates, go to step  21. If test light does not illuminate, go to step  22.
  12. Connect a 15-amp fused jumper wire between the battery positive voltage circuit and fuel pump supply circuit in fuel pump relay cavity. If the fuel pump operates, go to step  18. If fuel pump does not operate, go to next step.
  13. Disconnect fuel pump harness in-line connector located near the fuel tank. Test the fuel pump supply voltage circuit for an open or for high resistance between the fuel pump relay and the in-line connector. See Fig 2. Did you find and correct an open or high resistance in the fuel pump supply voltage circuit? If yes, go to step  26. If no, go to next step.
    14. NOTE: Inspect fuel pump ground circuit for being tight, corrosion on terminals, or damage to wiring harness.
  14. Test the fuel pump ground circuit for an open or for high resistance between the body pass through connector and ground. Did you find and correct and open or high resistance in the fuel pump ground circuit? If yes, go to step  26. If no, go to next step.
  15. Test for an intermittent and/or a poor connection at the fuel pump in-line connector to the body pass through connector. See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article. Did you find and correct and intermittent condition? If yes, go to step  26. If no, go to next step.
  16. Lower fuel tank. Test or inspect fuel tank electrical harness for damage, a short to ground or an open. Did you find and repair any damage, a short or an open in the fuel tank harness? If yes, go to step  26. If no, go to step  23.
  17. Connect all disconnected components. Install a NEW fuel pump fuse. Command fuel pump ON using a scan tool. If fuel pump fuse is open, go to step  23. If fuse is not open, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article.
  18. Test for an intermittent and/or a poor connection at fuel pump relay. See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article. Did you find and correct an intermittent condition? If yes, go to step  26. If no, go to step  24.
  19. Test for an intermittent and/or a poor connection at the harness of the Engine Control Module (ECM). See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article. Did you find and correct an intermittent condition? If yes, go to step  26. If no, go to step  25.
  20. Repair short to voltage in fuel pump supply voltage circuit. After repairs are complete, go to step  26.
  21. Repair open in fuel pump relay battery positive voltage circuit. After repairs are complete, go to step  26.
  22. Repair open or short to ground in the fuel pump fuse battery positive voltage circuit. After repairs are complete, go to step  26.
    23. NOTE: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.
  23. Replace right fuel pump/sender assembly. See FUEL PUMP/SENDER ASSEMBLY under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article. Replace fuel pump fuse if necessary. After repairs are complete, go to step  26.
  24. Replace fuel pump relay. After repairs are complete, go to step  26.
  25. Replace ECM. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - CTS article. After repairs are complete, go to next step.
  26. Operate the system in order to verify the repair. If fuel pump operates properly, system is okay. If fuel pump does not operate properly, go to step  2.
Fig 1: Locating & Identifying Rear Fuse Blocks
G00252315Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying Fuel Tank-To-Body Harness In-Line Connector
G00252316Courtesy of GENERAL MOTORS CORP.
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