DTC P0420: Catalyst System Efficiency Below Threshold (CALIF. Emissions): Notes

NOTE: Bank No. 1 refers to bank which includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Air/Fuel (A/F) sensor refers to sensor closest to engine block. Heated oxygen sensor No. 2 refers to sensor farthest from engine block.

NOTE: For component location, see appropriate illustration in THEORY & OPERATION article.