DTC P0420: Catalyst System Efficiency Below Threshold: Notes

NOTE: Heated oxygen sensor No. 1 is located on exhaust pipe in front of catalytic converter and may be referred to as bank No. 1 sensor No. 1. Heated oxygen sensor No. 2 is located on exhaust pipe in behind catalytic converter and may be referred to as bank No. 1 sensor No. 2.

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