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Home >> Cadillac >> 2000 >> Seville STS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 4.6L >> Diagnostic Tests >> DTC P0442: EVAP System Small Leak Detected >> 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 P0440, P0443, P0446, P0449, P0452, P0453, P0461, P0462, P0463 and P1441 are present. If any of these DTCs are present, diagnose affected DTCs first. If any of these DTCs are not 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  16. If no problems were found, go to next step.
  4. Ensure battery voltage is 10-17.5 volts, fuel level 3-18 gallons, and ECT at 122°F (50°C). Using scan tool, review and record FREEZE FRAME and FAIL RECORDS data. Clear DTCs. Perform SERVICE BAY TEST for EVAP system. If vehicle passes service bay test, fault is intermittent. See DIAGNOSTIC AIDS . If vehicle does not pass the service bay test, go to next step.
  5. Turn ignition off. Disconnect EVAP purge and vent lines from canister. Plug purge and vent line fittings on canister. Install fill tank cap adaptor to fuel fill neck and fuel fill cap. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to fuel tank cap adaptor. Ensure gauges on diagnostic station are zeroed before starting with test. Pressurize system to 5 in. Hg. If pressure can be obtained and held, go to step  7. If pressure cannot be obtained or held, go to next step.
  6. Check for poor fuel vapor line connections at canister and/or fuel tank. Check for leaking or damaged fuel vapor line or for leaking/damaged fuel sender assembly to fuel tank "O" ring. Repair as necessary. After repairs, go to step  16. If no problems were found, go to step  11.
  7. Install a hand-held vacuum pump to EVAP vent line. Using scan tool, command EVAP vent valve on (closed). Using vacuum pump, apply 5 in. Hg. If vacuum can be obtained and held, go to step  9. If vacuum cannot be obtained and held, go to next step.
  8. Connect vacuum pump to EVAP purge valve. Using scan tool, command EVAP vent valve on (closed). Using vacuum pump, apply 5 in. Hg. If vacuum can be obtained and held, go to step  12. If vacuum cannot be obtained and held, go to step  13.
  9. Connect vacuum pump to EVAP purge valve and apply 5 in. Hg. If vacuum can be obtained and held, go to step  14. If vacuum cannot be obtained and held, go to next step.
  10. Check for incorrect EVAP purge valve to throttle body or manifold. Check for EVAP purge valve "O" ring. Repair as necessary. After repairs, go to step  16. If no problem is found, go to step  15.
  11. Replace EVAP canister. After replacing canister, go to step  16.
  12. Replace EVAP vent line. After replacing vent line, go to step  16.
  13. Replace EVAP vent valve. After replacing vent valve, go to step  16.
  14. Replace EVAP purge line. After replacing purge line, go to step  16.
  15. Replace EVAP purge valve. After replacing purge valve, go to next step.
  16. 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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