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Home >> Cadillac >> 2000 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 4.6L >> Diagnostic Tests >> DTC P0440: EVAP System >> Diagnostic Procedures
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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. Using scan tool, check if DTCs P0442, P0443, P0446, P0449, P0452, P0453, P0461, P0462 and P0463 are present. If any of these DTCs are present, diagnose affected DTCs first. If none of these DTCs are present, go to next step.
  3. Check for loose, incorrect, defective or missing fuel filler cap. Check for misrouted, kinked or damaged EVAP system purge lines. Repair as necessary. After repairs, go to step  21. If no problems were found, go to next step.
  4. Ensure battery voltage is 10.5-17.5 volts, fuel level 3-18 gallons, and ECT less than 122°F (50°C). Using scan tool, review and record FREEZE FRAME and FAIL RECORDS data. Clear DTCs. Using scan tool, perform SERVICE BAY TEST for EVAP system. If vehicle passes service bay test, see DIAGNOSTIC AIDS . If vehicle does not pass the service bay test, go to next step.
  5. Disconnect vacuum source from EVAP purge solenoid. Using scan tool, observe fuel tank pressure sensor display. If fuel tank pressure is about zero in. H2O, go to step  8. If fuel tank pressure is not about zero in. H2O, go to next step.
  6. Leave fuel vapor line disconnected. Remove fuel filler cap. Using scan tool, observe fuel tank pressure sensor display. If fuel tank pressure is about zero in. H2O, go to next step. If fuel pressure reading is not about zero in. H2O, diagnose using DTC P0453 test. See DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT HIGH VOLTAGE .
  7. Repair cause of blocked/restricted fuel vapor line. After repairs, go to step  21.
  8. Reconnect fuel vapor line to canister. Disconnect purge and vent lines at canister. Plug purge and vent line fittings on canister. Install Fill Tank Adaptor to fuel fill neck and fuel cap. Connect EVAP Pressure/Purge Diagnostic Station (J-41413). Ensure gauges on test equipment is zeroed before starting test. Pressurize system to 5 in. H2O. If pressure can be obtained, go to next step. If pressure cannot be obtained, go to step  14.
  9. If scan tool displays fuel tank pressure sensor at 5 in. H2O, go to next step. If scan tool does not display fuel tank pressure at 5 in. H2O, diagnose using DTC P0452 test. See DTC P0452: FUEL TANK PRESSURE SENSOR CIRCUIT LOW VOLTAGE .
  10. Disconnect fuel vapor line. Plug fuel vapor line fitting on canister. Reconnect EVAP vent line to canister. Connect a hand-held vacuum pump to purge line fitting on canister. Turn ignition on, with engine off. Using scan tool, command EVAP vent valve on (closed). Using vacuum pump, apply 5 in. Hg. If 5 in. Hg can be obtained, go to next step. If 5 in. Hg cannot be obtained, go to step  12.
  11. Command EVAP vent valve off (open). Observe vacuum reading on vacuum pump. If vacuum drops to zero in. Hg, go to step  15. If vacuum does not drop to zero in. Hg, go to step  18.
  12. Leave vacuum pump connected. Disconnect EVAP vent line from canister. Plug vent valve fitting on canister. Using vacuum pump, apply 5 in. Hg. If vacuum can be obtained and held, go to next step. If vacuum cannot be obtained and held, go to step  18.
  13. Check EVAP vent line for damage. Repair as necessary. After repairs, go to step  21. If no problem is found, go to step  19.
  14. Check for leaking fuel filler neck/hoses, fuel vapor line or leaking fuel sensor assembly seal. Repair as necessary. After repairs, go to step  21. If no problems were found, go to step  18.
  15. Disconnect EVAP purge line from EVAP purge valve. Connect vacuum gauge to EVAP purge valve. Start and operate engine at idle. Using scan tool, command EVAP system to 100 percent purge. If vacuum gauge indicates greater than 12 in. Hg, go to next step. If vacuum gauge does not indicate greater than 12 in. Hg, go to step  17.
  16. Repair cause of blocked/restricted EVAP purge line. After repairs, go to step  21.
  17. Check for blocked/restricted vacuum source to EVAP purge valve. Repair as necessary. After repairs, go to step  21. If no problem is found, go to step  20.
  18. Replace EVAP canister. After replacing canister, go to step  21.
  19. Replace EVAP vent valve. After replacing vent valve, go to step  21.
  20. Replace EVAP purge valve. After replacing purge valve, go to next step.
  21. Using scan tool, review and record FREEZE FRAME and FAIL RECORDS data. Clear DTCs. Operate vehicle within parameter for setting this DTC. Using scan tool, monitor SPECIFIC DTC INFO for this DTC until test runs. If scan tool indicate that this DTC failed this ignition, go to step  2. If scan tool does not indicate that this DTC failed this ignition, system is okay.
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