Q: Code P0420. Need to replace catalytic converter.

asked by on January 03, 2017

Need to replace catalytic converter

My car has 11800 miles.
My car has an automatic transmission.

Hi there. The code P0420 is coming up for the Downstream Oxygen sensor has picked up an abnormal reading and is saying that the catalytic converter is below threshold. There could be a misfire on the engine, leaking injector, ignition timing retard, engine coolant temperature sensor not working, a leak in the exhaust system, a faulty Oxygen Sensor, or a faulty catalytic converter. Before replacing the catalytic converter, I recommend checking all of the above information and see if your engine is having an issue. If there is no misfire, the injectors are replaced or cleaned, the ignition is normal, the coolant temperature sensor is working, there is no leaks in the exhaust system, and the Oxygen sensors check out to be good, then I recommend replacing the catalytic converter. If you need further assistance with your check engine light being on, then seek out a professional, such as one from Your Mechanic, to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

How many catalytic convertors are on my 2010 buick lacrosse

Hi Sade. Thanks for contacting us today. To my knowledge, the 2010 Buick LaCrosse is a dual-system catalytic converter set-up. In most cases, when one wears out, the other one is quick to follow.

Sudden loss of acceleration when driving

Your car is equipped with a continuously variable transmission (CVT). The CVT has sensors to keep if from overheating and dropping to a low fluid level. When the transmission detects an issue, it will go into limp home mode to...

Brakes locked up

When the rotors get this hot, this is usually an indication that the brake pads are dragging on the rotors. This can happen when the brake calipers are misaligned on the rotors. This problem is often compounded when, as a...

Related articles

Top 10 Best-Selling Cars of 2016
Ford F-series pickup trucks, Toyota Camry, and Honda Civic are some of the best-selling cars of 2016 and all deliver on reliability and efficiency.
The Top 5 Selling Cars in Alabama in 2012
2012 2012 was a great year in Alabama for auto manufacturing, but that wasn’t the only bright spot. Vehicle sales in Alabama were also robust in 2012. Nothing much changed in terms of the vehicle types that were most popular...
The Best Used Cars to Buy If You're a Gardener or Landscape Architect
Gardeners Gardeners and landscape architects need to haul around quite a bit of gear. As a gardener, chances are you will need to transport a variety of mowing equipment, along with smaller implements. You may also need to move shrubs,...