Question 1

What is the P0420 code definition?

Accepted Answer

Catalyst System Efficiency Below Threshold Bank 1

Question 2

What are the P0420 code symptoms?

Accepted Answer

Check engine light, excessive exhaust smell, poor fuel economy, or low engine power

Question 3

What causes P0420 code?

Accepted Answer

Failed catalytic converter, malfunctioning oxygen (o2) or air/fuel (A/F) ratio sensor, exhaust leaks, and inferior catalytic converter

Question 4

How to diagnose a P0420 DTC?

Accepted Answer

Preliminary testing, inspect exhaust, check oxygen (o2) or air/fuel (A/F) ratio sensor operation, and generic switch-ratio scan tool test

Question 5

How do I repair a P0420 DTC?

Accepted Answer

While replacing the catalytic converter is often the fix for a P0420 code, it does not solve the root cause of why the catalytic converter failed and repeat failure is likely. If a bad catalytic converter is suspected, make sure to determine the root cause of failure before replacing it. This is the only way to guarantee an accurate repair and avoid a costly repeat catalytic converter failure.

Question 6

Can I still drive my car with a P0420 code?

Accepted Answer

It is not recommended to drive your vehicle with a P0420 code set. While your vehicle may seem to operate normally, driving your vehicle with a P0420 code can rob your engine of horsepower and fuel economy. It will also raise your vehicles emissions output and cause your vehicle to fail a state inspection or smog test.