Which trouble codes do owners report?

P0420 Catalyst System Efficiency Below Threshold leads at 64.

Trouble codes owners quote in complaints about this part. P0420 Catalyst System Efficiency Below Threshold: 64; P0430 Catalyst System Efficiency Below Threshold: 23.

The code owners quote most is P0420. Read your own code from a scan and give the shop the exact code, not only "the light is on".

Source: NHTSA owner complaint files · file downloaded 2026-10-05

Data and chart by CalcScrape: Catalytic Converter Replacement Cost Calculator