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Home >> Cadillac >> 1998 >> Catera >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0440 - EVAP System >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then go to next step.
  2. If DTCs P0443 or P0446 are also set, go to applicable DTC. If DTCs P0443 or P0446 are not set, go to next step.
  3. Inspect EVAP system for disconnected, kinked or deteriorated hoses and lines. Check for loose hose connections or missing or loose fuel cap. Inspect for obvious damage to any system component. Repair components as necessary, then go to step 23). If components are okay, go to next step.
  4. Disconnect manifold vacuum source hose at purge valve. Connect a vacuum gauge to manifold vacuum source hose. EVAP Pressure/Purge Diagnostic Station (J-41413) can be used for this purpose, if necessary. Start and operate engine to greater than 2000 RPM. Observe source vacuum level. If vacuum gauge indicates 15 in. Hg, go to next step. If vacuum gauge does not indicate 15 in. Hg, go to step 16).
  5. Turn ignition off. Remove fuel cap. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure. If fuel tank pressure is minus one to plus one inch H2O, go to next step. If fuel tank pressure is not minus one to plus one inch H2O, go to DTC P0450.
  6. Zero gauges on EVAP Pressure/Purge Diagnostic Station (J-41413) prior to installation. Connect pressure/purge diagnostic station to EVAP service port. Reinstall fuel cap. Plug EVAP vent hose or disconnect vent hose from vent valve and plug hose. Attempt to pressurize EVAP system using pressure/purge diagnostic station. Monitor pressure using gauge on EVAP pressure/purge diagnostic station. If pressure reading is 15 in. H2O, go to next step. If pressure reading is not 15 in. H2O, go to DTC P0455.
  7. Maintain EVAP system pressure at 15 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure is at or greater than 11 in. H2O, go to next step. If fuel tank pressure is not at or greater than 11 in. H2O, go to DTC P0450.
  8. Switch rotary switch on pressure/purge diagnostic station to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 10). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
  9. Unplug EVAP vent hose and/or reconnect vent hose at vent valve. Disconnect ECM connector located in engine compartment, in relay center. Remove main relay. Using fused jumper, connect between battery circuit and switched battery feed circuit at relay harness connector. Using another fused jumper, ground EVAP vent valve control circuit at ECM harness connector. This closes vent valve. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 18). If pressure does not drop to less than 10 in. H2O within 2 minutes, see DIAGNOSTIC AIDS.
  10. Disconnect fuel tank to EVAP canister vapor hose at canister and plug port on canister. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 14).
  11. Disconnect purge valve to EVAP canister vapor hose at purge valve and plug hose. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 17).
  12. Disconnect vent hose at EVAP canister and plug port on canister. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 20).
  13. Disconnect and plug purge hose at EVAP canister. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 21). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 19).
  14. Reconnect fuel tank vapor hose at EVAP canister. Disconnect fuel tank vapor hose at fuel tank and plug hose. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 22). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
  15. Reconnect fuel tank vapor hose at fuel tank. With EVAP pressure/purge diagnostic station connected to EVAP service port, continuously attempt to pressurize EVAP system by leaving control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J-41416), locate fuel tank system leaks. Check fuel tank, tank seams, fuel cap, fill pipe, sending unit, sending unit-to-tank seal, or fuel tank pressure sensor. Repair as necessary. After repairs, go to step 23).
  16. Check for damaged vacuum source hose, blocked or restricted manifold vacuum port or low engine vacuum. Repair as necessary. After repairs, go to step 23).
  17. Replace purge valve. After replacing valve, go to step 23).
  18. Replace vent valve. After replacing valve, go to step 23).
  19. Replace canister. After replacing canister, go to step 23).
  20. Replace vent hose. After replacing hose, go to step 23).
  21. Replace purge hose (valve-to-canister). After replacing hose, go to step 23).
  22. Replace vapor hose (tank-to-canister). After replacing hose, go to step 23).
  23. Ensure that vent valve is on (closed). Pressurize EVAP system to 15 in. H2O using EVAP pressure/purge diagnostic station. Monitor pressure using gauge on EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 6). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
  24. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0440 is set, go to step 2). If DTC P0440 is not set, go to next step.
  25. 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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