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Home >> Cadillac >> 1998 >> Catera >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0442 - EVAP System (Small Leak Detected) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then go to next step.
  2. If DTC P0441 or P0446 is also set, diagnose affected DTC first. If either DTCs are not set, go to next step.
  3. Check for disconnected, kinked or deteriorated hoses/lines. Check loose hose connections, missing or loose fuel tank filler cap. Repair as necessary. After repairs, go to step 23). If no problems were found, go to next step.
  4. Disconnect manifold vacuum source at purge valve. Install vacuum gauge to manifold vacuum source line. Start engine. Operate engine at greater than 2000 RPM and observe vacuum gauge. If vacuum gauge reads 15 in. Hg, go to next step. If vacuum gauge does not read 15 in. Hg, go to step 16).
  5. Turn ignition off. Remove fuel filler cap. Turn ignition on, engine off. Using scan tool, observe fuel tank pressure reading. If scan tool reads -1 to 1 in. H2O, go to next step. If scan tool does not read -1 to 1 in. H2O, diagnose using DTC P0450 diagnostics.
  6. Using EVAP Pressure/Purge Diagnostic Station (J 41413), connect diagnostic station to EVAP service port. Reinstall fuel filler cap. Disconnect ECM harness connector. Remove main relay. Using a fused jumper wire, connect jumper between battery voltage and ignition circuit in relay harness connector terminal. Using another fused jumper wire, ground EVAP vent valve control circuit in ECM harness connector (to close vent). Pressurize EVAP system using EVAP pressure/purge diagnostic station. Monitor pressure using gauge in diagnostic station. If 15 in. H2O can be achieved, go to next step. If 15 in. H2O cannot be achieved, diagnose using DTC P0455 diagnostics.
  7. Maintain system pressure at 15 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure is at 15 in. H2O or greater than 11 in. H2O, go to next step. If fuel tank pressure is not 15 in. H2O or not greater than 11 in. H2O, diagnose using DTC P0450 diagnostics.
  8. Switch rotary switch on diagnostic station to HOLD position 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, no problem is found. See DIAGNOSTIC AIDS.
  9. Disconnect and plug fuel tank vapor line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position 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).
  10. Disconnect and plug purge line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position 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).
  11. Disconnect and plug vent line at vent valve. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position 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 18).
  12. Disconnect and vent line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position 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 line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station 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 line at canister. Disconnect and plug fuel tank vapor line at fuel tank. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position 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-to canister vapor line at fuel tank. Continuously attempt to pressurize EVAP system by leaving diagnostic station control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J 41416), check fuel tank for leaks at seams, filler pipe, sending unit and tank pressure sensor. Repair as necessary. After repairs or after checking for leaks, go to step 23).
  16. Check for damaged vacuum source line, blocked or restricted vacuum port, or for low vacuum. Repair as necessary. After repairs, go to step 23).
  17. Replace purge valve. Check for contamination causing purge valve to fail. After replacing valve, go to step 23).
  18. Replace vent valve. After replacing valve, go to step 23).
  19. Replace EVAP canister. After replacing canister, go to step 23).
  20. Replace vent line. After replacing line, go to step 23).
  21. Replace vent-to-canister purge line. After replacing purge line, go to step 23).
  22. Replace vent-to-canister vapor line. After replacing vapor line, go to next step.
  23. Pressurize EVAP system to 15 in. H2O using EVAP Pressure/Purge Diagnostic Station (J 41413). Monitor pressure using gauge on diagnostic station. Switch rotary switch on diagnostic station to HOLD position. 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, select DTC, CLEAR INFO. Operate vehicle within the conditions for setting this DTC. Check for DTCs. If DTC P0442 is set, repeat step 5). If DTC P0442 is not set, go to next step.
  25. If additional undiagnosed DTCs are set, go to applicable DTC test. If no additional DTCs are set, system is okay.
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