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HOMESERVICE MANUALSBUICK1999REGAL LSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P0352-P0452DTC P0446DTC P0446: EVAP SYSTEM VENT VALVE PERFORMANCE (4.8L, 5.3L & 6.0L "C" & "K" SERIES)DIAGNOSTIC PROCEDURES
1999 Buick Regal LS

Diagnostic Procedures

1999 Buick Regal LSSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read FUEL TANK PRESSURE. If scan tool displays zero in. Hg, go to next step. If scan tool does not display zero in. Hg, perform fuel tank sensor circuit diagnosis. See DTC P0453 test.
  3. Inspect for improperly routed, kinked or damaged EVAP purge and tank vent lines. Repair as necessary. After repairs, go to step  13. If repairs were not necessary, go to next step.
  4. Ensure battery voltage is 10.5-17.5 volts, fuel level is 15-85 percent of full capacity and engine temperature is between 38-95°F (4-35°C). Check for loose, missing, defective or incorrect fuel tank cap. Check for incorrectly routed or defective EVAP system vacuum and vapor lines. Check for malfunctioning or damaged vapor canister or for charcoal release from canister. Using scan tool, perform EVAP system SERVICE BAY TEST. If system passed the test, see DIAGNOSTIC AIDS . If system did not pass the test, go to next step.
  5. Clear DTCs using scan tool. Turn ignition off. Disconnect fuel tank vapor and EVAP purge lines from EVAP vapor canister. Plug canister port for fuel tank vapor line. Connect a hand-held vacuum pump to EVAP purge line canister fitting. Turn ignition on, with engine off. Using scan tool, command EVAP vent valve ON (closed). Using vacuum pump, apply 5 in. Hg. Command EVAP vent valve OFF (open). Monitor vacuum pump gauge. If vacuum drops when vent valve is opened, go to step  8. If vacuum does not drop when vent valve is opened, go to next step.
  6. Leave system connected as in step  5. Disconnect and plug vent line at EVAP vent valve. Using vacuum pump, apply 5 in. Hg. Remove plug from vent line. Monitor vacuum pump gauge. If vacuum drops when vent line is unplugged, go to step  10. If vacuum does not drop when vent line is unplugged, go to next step.
  7. Inspect EVAP vent line from canister to vent valve for restrictions. Repair as necessary. After repairs, go to step  13. If restriction is not found, go to step  11.
  8. Inspect fuel tank vapor line for restriction. Repair as necessary. After repairs, go to step  13. If restriction is not found, go to next step.
  9. Install EVAP Pressure/Purge Diagnostic Station (J-41413). 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. Turn ignition on, with engine off. Using scan tool, command EVAP vent valve closed. Using Pressure/Purge Diagnostic Station, pressurize EVAP system. Allow system to stabilize (on scan tool) and then rotate diagnostic station's selector to OFF/HOLD position. Compare diagnostic station's pressure gauge and fuel tank pressure on scan tool. If fuel tank pressure sensor indicates actual amount of pressure in EVAP system, go to step  4. If fuel tank pressure sensor does not indicates the actual amount of vacuum in EVAP system, go to step  12.
  10. Replace EVAP vent valve. After replacing EVAP vent valve, go to step  13.
  11. Replace EVAP canister. After replacing EVAP canister, go to step  13.
  12. Replace fuel tank pressure sensor. After replacing pressure sensor, go to next step.
  13. Using scan tool, select DTC and CLEAR DTC INFO functions. Clear DTCs. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2.
  14. Using scan tool, select CAPTURE INFO and REVIEW INFO function. If any undiagnosed DTCs are set, go to appropriate DTC test.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.