Skip the auto shop - Our mechanics make house calls

Q: Bad O2 sensor

asked by on

I am getting code P0420. I think it is the O2 sensor, bank 1.

A: Hello, code P0420 represents right main cat...

Hello, code P0420 represents right main catalyst deterioration. There can be a few things that need to be checked before replacing parts. The intake system needs to be inspected for vacuum leaks and unmetered air leaks. The exhaust system should be checked for leaks, from the exhaust manifolds all the way to the oxygen sensor after the catalytic converter. A scanner should be connected and the oxygen sensor. After, the car should be monitored for voltage activity, and test to see if it can be driven rich and lean. The mostly likely failed part is the catalytic converter,but some people believe in trying an oxygen sensor first. I would have a mechanic inspect your vehicle and let you know if you need a oxygen sensor or catalytic converter replacement.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Q: Changed ignition switch now car will not start

Hi there: It really depends on why you changed the ignition switch as to why you're vehicle is not starting now. If the vehicle was not starting before, it's possible that the ignition switch was not the damaged component. If...

Q: O2 sensors changed, but check engine light still showing code after clearing it I checked fuse. Wires are good and used Denso OE.

Depending on what the code was for will determine if the oxygen sensor was to be replaced. If the conditions were for a rich or lean mixture and it said oxygen sensor, then the spark plugs and wires could need...

Q: Oil pressure light

Hello There, The oil pressure light will usually come on when a few things could be happening. Either the motor is in fact low on oil, the oil pump could be failing or the oil pressure sending unit is not...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.