DTC code P0420: Catalyst efficiency below threshold
P0420 means the catalytic converter isn’t cleaning exhaust gases as well as it should. The computer compares readings from the upstream and downstream oxygen sensors to figure that out. A failing converter is the classic cause, but a bad oxygen sensor or a misfire feeding raw fuel downstream sets off the same code. Most vehicles show no symptoms besides the warning light.
Intangles surfaces recurring O2 sensor or misfire codes on the same vehicle, so a technician can find the real cause before signing off on an expensive converter. Want to see how? Share your email to get started.
We’re looking forward to meeting you