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HOMESERVICE MANUALSCHEVROLET2001CAVALIER LS, 2.4 TREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 59 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCEDIAGNOSTIC PROCEDURES
2001 Chevrolet Cavalier LS, 2.4 T

Diagnostic Procedures

2001 Chevrolet Cavalier LS, 2.4 TSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  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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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.