Question 1

What does P0420 mean?

Accepted Answer

The P0420 code is triggered when the catalytic converter on Bank 1 is not operating at the expected efficiency level. The ECM monitors the oxygen sensor readings before and after the catalytic converter. When the converter is working properly, the downstream sensor should show a relatively stable signal. P0420 means the catalyst is aging or damaged and no longer effectively reducing emissions.

Question 2

What causes P0420?

Accepted Answer

Failing catalytic converter, Faulty downstream oxygen sensor, Engine misfire damaging catalyst, Oil burning into exhaust

Code P0420 — Efficacité du catalyseur sous le seuil (Banque 1)

Causes courantes

Codes associés