Q: P0420 code

asked by on

I noticed a few months ago my check engine light would go on and off. Now it stays on and I was told it won't pass smog. The code is p0420 "b1 cat system system below threshold."

I am curious to see if I can fix this problem or pass smog in ca without replacing. Also my spark plugs are in need of replacing I believe could that affect the codes? What would be your course of action if you need to pass smog with this code

My car has 171000 miles.
My car has an automatic transmission.

Hi there:

That’s a very tricky question to answer. In general, the P-0420 OBD-II error code indicates that there is a reduction of efficiency of the catalytic system for reducing emissions. This could be caused by O2 sensors, leaking fuel injectors, problems with the EGR system or the catalytic converter itself. Depending on which state you live, would dictate my corrective course of action as each US state has different emissions standards for passing. You might want to have one of our professional mechanic in your state complete a check engine light is on inspection; which will allow them to dig deeper in the ECU to see what specifically triggered this error code.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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

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: Check Engine light came on

Multiple lights may be caused by multiple problems.Your BMW has a few dozen computers which can trigger warning lights to appear on your dash. Diagnosing multiple problems may be time extensive, but can be performed by a qualified technician with...

Q: My car won't crank or start when I turn the key all the lights and everything else functions and when I take the key out the light

Hello, thank you for writing in. The starting system is not very complicated. When you are not getting a crank when starting, the battery, alternator, wiring, or ignition switch are typically bad. Most common to fail is the battery or...

Q: Should I use windshield washer fluid to defrost my front windshield 2016 Nissan Altima

Hi There, You can certainly use the window washer fluid in your car to spray on the windshield when defrosting your windshield. As you may know, most window washer fluid contain an alcohol solution in them that reduces the freezing...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...