Skip the auto shop - Our mechanics make house calls

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 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

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: Clutch won't go into gear

Having difficulty moving into first gear and then being unable to move your Subaru into any other gear leads me to believe that there are problems with one or more components in the clutch system. While the information you offered...

Q: when a front tire goes flat can the impact damage the steering gear

A flat tire would not create that type of damage to the steering gear. The previous noise that you had could have been related to steering gear. That has car has a steering rack assembly (gear). Unfortunately, I would need...

Q: engine light stays on even after replacing the intake valve selenoid the code is p0075

Diagnostic trouble code P0075 means there is a fault in the Intake Valve Control Solenoid Circuit. A defective solenoid is one possible cause of the code setting but problems in the circuit wiring are often the cause of the fault....

Related articles

What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
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.