Diagnosis & Repair
- Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P1431 exists, go to next step. If other DTCs exists, diagnose and repair those DTCs first and then retest.
- Check operation of vacuum sensor. See VACUUM SENSOR FOR HYDROCARBON ADSORBER CATALYST SYSTEM under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If vacuum sensor operates properly, check for restricted vacuum line to vacuum sensor and repair as necessary. If vacuum sensor does not operate properly, replace vacuum sensor.