Toyota P0420 (Catalyst System Efficiency Below Threshold, Bank 1) is the single most-searched Toyota fault code in the UK — and on Yaris, Auris, Corolla, C-HR and Prius it splits three ways: genuine cat wear at 120,000+ miles, a tired rear (downstream) lambda sensor that mimics cat failure, or straight catalytic-converter theft. Toyota hybrids remain the #1 stolen-cat target in Britain according to the AA and every major insurer.
Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email bob@bobsmechanicalrepairs.co.uk.