Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
EVAP Control System Diagnosis
1998 Buick RivieraSECTION EVAP Control System Diagnosis
NOTE:
Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.
- If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in TESTS W/CODES article.
- Turn ignition switch to LOCK position. Remove fuel filler cap. Connect scan tool to data link connector. Turn ignition switch to RUN position. Observe fuel tank pressure on scan tool. If fuel tank pressure is zero in. H2O, go to next step. If fuel tank pressure is not zero in. H2O, perform DTC P0453 test. See TESTS W/CODES article.
- Replace fuel filler cap. Using scan tool, command EVAP canister vent valve on. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP service port. Apply 5 in. H2O pressure to EVAP system while observing fuel tank pressure on scan tool. If fuel tank pressure is 5 in. H2O, go to next step. If fuel tank pressure is not 5 in. H2O, perform DTC P0452 test. See TESTS W/CODES article.
- Monitor EVAP pressure gauge on diagnostic station while commanding EVAP canister vent valve off. If EVAP pressure decreases to zero in. H2O within 5 seconds, go to next step. If EVAP pressure does not decrease to zero in. H2O within 5 seconds, perform DTC P0446 test. See TESTS W/CODES article.
- Start engine. Remove fuel filler cap. Using scan tool output test function, select SEAL SYSTEM and activate. Install fuel filler cap. Switch rotary switch on diagnostic station to PURGE. Run engine at idle while monitoring vacuum gauge on diagnostic station. If vacuum does not increase to greater than zero in. H2O, go to next step. If vacuum increases to greater than zero in. H2O, perform DTC P1441 test. See TESTS W/CODES article.
- Using scan tool output test function, select SYSTEM PERF and activate. Switch rotary switch on diagnostic station to PURGE. Run engine at 2500 RPM for at least 10 seconds while monitoring vacuum gauge on diagnostic station. If vacuum increases to greater than -5 in. H2O, system is okay at this time. If vacuum does not increase to greater than -5 in. H2O, perform DTC P0440 test. See TESTS W/CODES article.
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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.