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Home >> Chevrolet >> 2000 >> Prizm LSi, Standard >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls Self-Diagnostics - 1.8L >> Diagnostic Tests >> DTC P0451: Fuel Tank Pressure Sensor Performance >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Loosen fuel tank filler cap to release any pressure inside fuel tank. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure sensor parameter. If fuel tank pressure sensor parameter is within 0.0-0.5 in. H2O, go to next step. If fuel tank pressure sensor parameter is not within 0.0-0.5 in. H2O, go to step  4 .
  3. Using scan tool, clear DTC. Place vehicle into Check Mode using scan tool. Operate vehicle within Freeze Frame conditions. Recheck DTCs. If DTC resets, go to step  6 . If DTC does not reset, see DIAGNOSTIC AIDS  .
  4. Disconnect vapor pressure supply hose to FTP sensor. Turn ignition on, with engine off. Observe fuel tank pressure sensor parameter on scan tool. If fuel tank pressure sensor parameter is 0.0-0.5 in. H2O, go to next step. If fuel tank pressure sensor parameter is 0.0-0.5 in. H2O, go to  6 .
  5. Repair cause of trapped vapor pressure to fuel tank pressure sensor. Check for pinched, crushed or restricted EVAP lines and hoses. Check for blocked or restricted EVAP components. Check for faulty EVAP solenoids or EVAP canister. Repair as necessary. After repairs, go to step  14 .
  6. Turn ignition off. Disconnect fuel tank pressure sensor harness connector. Turn ignition on, with engine off. Using DVOM, check voltage of fuel tank pressure sensor reference voltage circuit at fuel tank pressure sensor harness connector. See WIRING DIAGRAMS article. If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step  8 .
  7. Using DVOM, check voltage of fuel tank pressure sensor input circuit at fuel tank pressure sensor harness connector. See WIRING DIAGRAMS article. If voltage reading is 4.9 volts, go to step  10 . If voltage reading is not 4.9 volts, go to step  9 .
  8. Check for an open or short in fuel tank pressure sensor reference voltage circuit between fuel tank pressure sensor and PCM. Repair as necessary, After repairs, go to step  14 . If circuit is okay, go to step  13 .
  9. Check for an open or short in fuel tank pressure sensor input circuit between fuel tank pressure sensor and PCM. Ensure fuel tank pressure sensor input circuit is not shorted to sensor ground circuit. Repair as necessary. After repairs, go to step  14 . If circuit is okay, go to step  13 .
  10. Using test light connected to battery voltage, probe fuel tank pressure sensor connector ground circuit (harness side). See WIRING DIAGRAMS article. If test light illuminates, go to step  12 . If test light does not illuminate, go to next step.
  11. Check for an open in fuel tank pressure sensor ground circuit between fuel tank pressure sensor and PCM. Repair as necessary, After repairs, go to step  14 . If circuit is okay, go to step  13 .
  12. Replace fuel tank pressure sensor. After replacing sensor, go to step  14 .
  13. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTC(s).
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