Toyota Avalon (XX50) 2019-2022 Service & Repair Manual > Sfi System: Catalyst System Efficiency Below Threshold Bank 1 (P042000)
MONITOR DESCRIPTION The ECM uses air fuel ratio sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency. The first sensor, the air fuel ratio sensor (sensor 1), sends pre-catalyst information to the ECM. The second sensor, the air fuel ratio sensor (s ...
