DTC P0420: Catalyst System Efficiency Below Threshold: Notes

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Heated A/F sensors are located on each exhaust manifold. Heated A/F sensor on rear (firewall side) exhaust manifold may also be referred to as bank No. 1 sensor No. 1. Heated A/F sensor on front (radiator side) exhaust manifold may also be referred to as bank No. 2 sensor No. 1. A/F sensors may also be referred to as A/F ratio sensors.