Skip the auto shop - Our mechanics make house calls

Q: Check engine light code P0420

asked by on

my check engine light came on after I filled gas. I got the code read and it was the code P0420 for catalytic converter. However, after I drove it a couple times the light went off. I filled gas, it went back on and as before after driving a couple times it went off. Why would it be going on and off if there was a problem?

My car has 65000 miles.
My car has an automatic transmission.

You may have a purge valve that is leaking and causing excessive fumes to enter the intake manifold during the refuel process. When you start the vehicle, the excessive rich mixture may be causing the catalyst to overheat which will trigger the P0420 code. This will happen if, after a couple of starts, the computer does not see a problem and clears the code.

I’d recommend seeking some assistance from a certified mechanic who can diagnose your Check Engine Light first hand and fix the problem accordingly.

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!
  1. Home
  2. Questions
  3. Check engine light code P0420

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: my engine went out in m camaro and im wondering could i ut a 5.3l engine out of a tahoe or silverado or impala ss in replace

It is probably "possible" to re-configure the mounts, axles, drivetrain, suspension and so forth in order to accommodate an engine other than the one the car was designed for. You would have to add to that workload though, the need...

Q: wont shift and runs rough, 2001 Ford Winstar

Your cluster may have a problem and is causing the transmission to not shift correctly. The car running rough may be due to a different issue. You should have a mechanic first find the reason for the cluster going haywire...

Q: How do you operate the manual transmission?

If your vehicle is equipped with a manual transmission, you have the ability to select the gear you want on your own (the transmission doesn’t work automatically). You’ll need to shift gears while driving according to your speed and performance...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...