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Home >> Cadillac >> 1998 >> Catera >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0450 - EVAP Fuel Tank Pressure Sensor Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then go to next step.
  2. Turn ignition on, with engine off. Remove fuel cap. Using scan tool, monitor fuel tank pressure voltage. If voltage is 2.2-2.8 volts, go to next step. If voltage is not 2.2-2.8 volts, go to step 6).
  3. Zero gauges on EVAP Pressure/Purge Diagnostic Station (J 41413) prior to installation. Connect diagnostic station to EVAP service port. Reinstall fuel cap. Disconnect vent hose at EVAP vent valve and plug hose. Using diagnostic station, pressurize EVAP system to 15 in. H2O. Monitor pressure using gauge on EVAP pressure/purge diagnostic station. Using scan tool, monitor fuel tank pressure sensor voltage. If sensor voltage is 3.3-3.9 volts, go to next step. If sensor voltage is not 3.3-3.9 volts, go to step 6).
  4. Turn ignition on, with engine off. Wiggle fuel tank pressure sensor electrical connector, wiring harness and ECM harness connector while observing scan tool display. If voltage value displayed on scan tool changes when wiggling components, go to step 17). If voltage value displayed on scan tool does not change when wiggling components, go to next step.
  5. Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0450 is set, go to next step. If DTC P0450 is not set, see DIAGNOSTIC AIDS.
  6. Disconnect fuel tank pressure sensor connector. Using DVOM, check voltage between ground and sensor harness connector signal circuit. If voltage is 4.7-5.3 volts, go to step 10). If voltage is not 4.7-5.3 volts, go to next step.
  7. Turn ignition off. Leave sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and sensor harness connector signal circuit. If any voltage is present, go to step 21). If no voltage is present, go to next step.
  8. Using DVOM, check harness continuity of sensor signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 22).
  9. Using DVOM, check harness continuity between ground and sensor signal circuit. If continuity is present, go to step 23). If continuity is not present, go to step 27).
  10. Using DVOM, check voltage between ground and sensor harness connector 5-volt reference circuit. If DVOM voltage is 4.7-5.3 volts, go to step 14). If voltage is not 4.7-5.3 volts, go to next step.
  11. Turn ignition off. Leave sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and sensor connector 5-volt reference circuit. If voltage is present, go to step 18). If no voltage is present, go to next step.
  12. Using DVOM, check harness continuity of sensor 5-volt reference circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
  13. Using DVOM, check harness continuity between ground and sensor 5 volt reference circuit. If continuity is present, go to step 20). If continuity is not present, go to step 27).
  14. Turn ignition off. Using DVOM, check resistance between ground and sensor harness connector ground circuit. If resistance is 0-5 ohms, go to step 16). If resistance is not 0-5 ohms, go to next step.
  15. Leave sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of sensor ground circuit. If continuity is present, go to step 27). If continuity is not present, go to step 24).
  16. Turn ignition on, with engine off. Using scan tool, monitor sensor voltage. Using a fused jumper wire, jumper sensor harness connector signal circuit to ground circuit. If scan tool display indicates zero volts, go to step 25). If scan tool does not indicate zero volts, go to step 28).
  17. Repair harness and connections as necessary. After repairs, go to step 29).
  18. Repair short to voltage in 5 volt reference circuit. After repairs, go to step 29).
  19. Repair open or high resistance in 5 volt reference circuit. After repairs, go to step 29).
  20. Repair short to ground in 5 volt reference circuit. After repairs, go to step 29).
  21. Repair short to voltage in signal circuit. After repairs, go to step 29).
  22. Repair open or high resistance in signal circuit. After repairs, go to step 29).
  23. Repair short to ground in signal circuit. After repairs, go to step 29).
  24. Repair open or high resistance in ground circuit. After repairs, go to step 29).
  25. Check for poor connections and terminal tension at fuel tank pressure sensor harness connector. Repair as necessary. After repairs, go to step 29). If connections and terminals are okay, go to next step.
  26. Replace fuel tank pressure sensor. After replacing tank pressure sensor, go to step 29).
  27. Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 29). If connections and terminals are okay, go to next step.
  28. Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
  29. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0450 is set, go to step 2). If DTC P0450 is not set, go to next step.
  30. If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.
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