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Home >> Cadillac >> 1998 >> Eldorado Base >> 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. Using scan tool, check if DTCs P0440, P0446, P0452, P0453, P0461, P0462, P0463, P1441, P1645 and P1646 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. If no problems were found, go to next step.
  4. Ensure battery voltage is 10.5-17.5 volts, fuel level 1.8-16.6 gallons, and engine temperature at 37-95°F (4-35°C). Using scan tool, record data stored when DTC was set. Clear DTCs. Using scan tool, perform SERVICE BAY TEST for EVAP system. If vehicle passes service bay test, fault is intermittent. If vehicle does not pass the service bay test, go to next step.
  5. Turn ignition off. Disconnect EVAP purge line from EVAP purge solenoid valve. Connect a hand-held vacuum pump to purge connection of EVAP purge solenoid valve. Using vacuum pump, apply vacuum. If 12 in. Hg of vacuum can be obtained and held, go to next step. If 12 in. Hg of vacuum cannot be obtained or held, go to step 10).
  6. Turn ignition off. Reconnect EVAP purge solenoid valve lines. Disconnect fuel tank vapor and EVAP purge line from EVAP vapor canister. Plug canister fitting for fuel tank vapor line. Connect a hand-held vacuum pump to EVAP purge line canister fitting. Turn ignition on. Using scan tool, command EVAP vent valve closed. Using vacuum pump, apply vacuum. If 5 in. Hg of vacuum can be obtained and held, go to step 9). If vacuum cannot be obtained and held, go to next step.
  7. Leave system connected. Disconnect vent line at EVAP vent valve. Plug vent line. Using vacuum pump, apply vacuum. If 5 in. Hg of vacuum can be obtained and held, go to step 11). If vacuum cannot be obtained and held, go to next step.
  8. Inspect EVAP vent line from canister to vent valve for leaks. Replace if necessary. If vent line is okay, go to step 12).
  9. Install EVAP Pressure/Purge Diagnostic Station (J 41413) and Ultrasonic Leak Detector (J 41416). Ensure gauges on test equipment is zeroed before starting test. Turn ignition off. Remove hand-held vacuum pump. Reconnect EVAP vapor canister purge and tank vent lines. Connect diagnostic station to EVAP system service port. Using scan tool, command EVAP vent valve closed. Continuously attempt to pressurize EVAP system by leaving EVAP Pressure/Purge Diagnostic Station control knob to PRESSURIZE position. Using ultrasonic leak detector, locate EVAP system leak. Repair as necessary. If leak is not present, go to step 13).
  10. Check EVAP purge solenoid valve and purge line for carbon contamination. Replace EVAP purge solenoid valve.
  11. Replace EVAP vent valve.
  12. Replace EVAP vapor canister.
  13. Relieve all system pressure. Using scan tool, use Purge/Seal function to turn EVAP purge solenoid valve on to varying vacuum levels with engine running and quickly seal system with scan tool. Leaving EVAP purge solenoid valve on for higher percents or longer times will allow a higher amount of vacuum to develop. A maximum of 12 in. H2O of vacuum can be applied to EVAP system using scan tool. While system is sealed, compare EVAP pressure/purge diagnostic station's vacuum gauge to vacuum shown on scan tool from the EVAP fuel tank pressure sensor. Allow a few seconds for system to stabilize. If both values are within 2 in. H2O of each other, repeat step 3). If both values are not within 2 in. H2O of each other, go to next step.
  14. Replace EVAP pressure sensor.
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