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Home >> Pontiac >> 2003 >> Vibe Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics >> Diagnostic Tests >> DTC P0451: Fuel Tank Pressure Sensor Performance >> Diagnostic Procedures
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Diagnostic Procedures

  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.
  2. Loosen fuel tank filler cap to release any pressure inside fuel tank. Turn ignition switch to RUN position, engine OFF. Observe fuel Tank Pressure Sensor (FTP) parameter on scan tool. Is FTP sensor parameter 0.0-0.5 in H2O? If yes, go to next step. If no, go to step  4.
  3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE using scan tool. Refer to SERVICE BAY TESTS  under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as noted. Does the DTC P0451 set? If yes, go to step  6. If no, go to DIAGNOSTIC AIDS .
  4. Remove FTP sensor. Connect FTP sensor harness connector. Turn ignition switch to RUN position, engine OFF. Observe FTP sensor parameter on scan tool. Is FTP sensor parameter 0.0-0.5 in. H2O? If yes, go next to step. If no, go to  6.
  5. Repair the cause of trapped vapor pressure in fuel tank. After repair, go to step  16.
  6. Turn ignition OFF. Disconnect FTP sensor 3-pin harness connector. Turn ignition switch to RUN position, engine OFF. Use a DMM to measure FTP sensor connector reference circuit voltage (harness side). Does the voltage equal 5 volts? If yes, go to next step. If no, go to step  8.
  7. Connect test light to reference voltage circuit and ground. Turn ignition switch to RUN position, engine OFF. Does the test light illuminate at least dimly? If yes, go to step  9. If no, go to step  14.
  8. Repair open in FTP sensor reference voltage circuit between sensor and splice SP108. After repair, go to step  16.
  9. Measure FTP sensor input circuit voltage (harness side). Is the voltage near 4.9 volts? If yes, go to step  11. If no, go to next step.
  10. Check FTP sensor input circuit for high resistance. Repair as necessary. Was a repair necessary? If yes, go to step  16. If no, go to step  15.
  11. Using a test light connected to battery voltage, probe FTP sensor ground circuit (harness side). Does the test light illuminate? If yes, go to step  13. If no, go to next step.
  12. Repair open in FTP sensor ground circuit between sensor and splice in the sensor ground circuit. After repair, go to step  16.
  13. Replace FTP sensor. After repair, go to step  16.
  14. Repair high resistance in reference voltage circuit of FTP sensor. After repair, go to step  16.
  15. Replace PCM. After repair, go to next step.
  16. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within CONDITIONS FOR RUNNING DTC  or until EVAP test is complete. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  17. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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