Toyota Avalon Service & Repair Manual > Sfi System: Catalyst System Efficiency Below Threshold Bank 1 (P042000,P043000)
MONITOR DESCRIPTION The ECM uses 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, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst informat ...
