What Lexus codes (P0420) actually mean on Lexus engines — the real cause, the common misdiagnosis, and the honest UK repair cost.
These are the OBD fault codes we see most often on Lexus vehicles in the workshop, with the real cause on Lexus engines rather than the generic textbook definition, plus the honest independent-garage cost.
Lexus fault codes explained
- P0420 — Catalyst efficiency on Lexus — IS/RX V6/V8 cat ageing, rear O2 sensor failures common (shared Toyota platform). Typical UK cost £180–£1500.
Codes are generic across manufacturers, but the fix is not. The same code on a Lexus usually points at a different component than it would on another make, which is why a make-specific diagnosis saves money before any parts are bought.