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Home >> Isuzu >> 2003 >> Rodeo LSE, 2.2 D >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Fuel System >> Fuel Pump Electrical Circuit Diagnosis (Ascender 4.2L) >> Testing Procedure

Testing Procedure

  1. Perform the DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - ASCENDER 4.2L article. When the check is complete, go to the next step.
  2. Turn ignition on, with engine off. Command the fuel pump relay ON and OFF with a scan tool. Repeat the commands and necessary. If the fuel pump goes ON and OFF, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If the fuel pump does not turn ON and OFF, go to next step.
  3. Command the fuel pump relay ON and OFF with a scan tool. Do you hear the fuel pump relay click when you command the fuel pump relay ON and OFF? If yes, go to step  10 . If no, go to next step.
  4. Turn ignition off. Remove the fuel pump relay. Turn ignition on, with engine off. Probe the control circuit of the fuel pump relay with a test lamp that is connected to a good ground. Command the fuel pump relay ON and OFF with a scan tool. If the lamp turns ON and OFF, go to next step. If the lamp does not turn ON and OFF, go to step  6 .
  5. Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the fuel pump relay. Command the fuel pump relay ON and OFF with a scan tool. If the test lamp turns ON and OFF, go to step  19 . If the test lamp does not go ON and OFF, go to step  22 .
  6. Does the test lamp remain illuminated with each command? If yes, go to next step. If no, go to step  8 .
  7. Test the control circuit of the fuel pump relay for a short to voltage. Did you find and correct the condition? If yes, go to step  27 . If no, go to step  26 .
  8. Test the control circuit of the fuel pump relay for a short to ground or an open. Did you find and correct the condition? If yes, go to step  27 . If no, go to step  20 .
  9. Turn ignition on, with engine off. Does the fuel pump operate continuously? If yes, go to next step. If no, go to step  11 .
  10. Turn ignition off. Remove the fuel pump. Turn ignition on, with engine off. Does the fuel pump operate continuously? If yes, go to step  21 . If no, go to step  25 .
  11. Inspect the PCM "B" fuse. Is the fuse open? If yes, go to next step. If no, go to step  14 .
  12. Test the supply voltage circuit of the fuel pump for a short to ground between the PCM "B" fuse and the fuel pump. Replace the PCM B fuse if necessary. Did you find and correct the condition? If yes, go to step  27 . If no, go to next step.
  13. Connect all disconnected electrical components. Install a new PCM "B" fuse. Command the fuel pump relay ON with a scan tool. Inspect the PCM B fuse. Is the PCM B fuse open? If yes, go to step  24 . If no, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
  14. Turn ignition off. Remove the fuel pump relay. Turn ignition on, with engine off. Probe the Ignition 1 voltage circuit of the fuel pump relay, switch side with a test lamp that is connected to a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  23 .
  15. Connect a 20-amp fused jumper wire between the ignition 1 voltage circuit of the fuel pump relay and the supply voltage circuit of the fuel pump relay and the supply voltage circuit of the fuel pump. Does the fuel pump operate? If yes, go to step  19 . If no, go the next step.
  16. Test the supply voltage circuit of the fuel pump for an open or high resistance between the fuel pump relay and the fuel pump. Did you find and correct the condition? If yes, go to step  27 . If no, go to next step.
    17. NOTE: Inspect the ground circuit for correct tightening, corrosion on the terminals, or damage to the wiring harness.
  17. Test the ground circuit of the fuel pump for an open or high resistance. Did you find and correct the condition? If yes, go to step  27 . If no, go to next step.
  18. Test for an intermittent and for a poor connection at the fuel sender cover. Did you find and correct the condition? If yes, go to step . 27 . If no, go to step  24 .
  19. Test for an intermittent and for a poor connections at the fuel pump relay. Did you find and correct the condition? If yes, go to step  27 . If no, go to step  25 .
  20. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  27 . If no, go to step  26 .
  21. Repair the short to voltage in the supply voltage circuit of the fuel pump. Verify the repair. Go to step  27 .
  22. Repair the open or high resistance in the ground circuit of the fuel pump relay. Verify repair. Go to step  27 .
  23. Repair the open in the ignition 1 voltage circuit of the fuel pump relay. Verify repair. Go to step  27 .
    24. NOTE: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.
  24. Replace the fuel sender. Replace the PCM "B" fuse if necessary. Verify repair. Go to step  27 .
  25. Replace the fuel pump relay. Verify repair. Go to step  27 .
  26. Replace the PCM. Verify repair. Go to step  27 .
  27. Operate the system in order to verify the repair. Did you correct the condition? If yes, system okay. If no, go to step  2 .
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