Reading
No make or model yet. The reading below is the shared meaning, not a note about one car.
The first look at a new code takes a moment. We open public pages and keep only what they say. We do not guess.
That is the reading. Another code?
P0420
Get it soonThe car compared sensors before and after the part that cleans the exhaust. It decided that part is not working well enough.
The light is asking for a shop visit. Driving a short way is often possible, but waiting can hide a real problem or make the next repair larger.
Shared powertrain name. A brand-owned code on the same car can mean something else.
A shop will typically confirm the code, look at related fuel, ignition, and oxygen-sensor data, and inspect the exhaust path before naming a part.