I am driving a 2008 lexus is250 awd. I got a check engine light pop up as I was driving.







I scanned the obd code and it gave me this error p0420. what could this be?

 

When you have a "Check VSC" it usually has something to do with emissions. Loose gas cap, bad sensor (MAF, O2), etc.

Sometimes when you get it scanned the code P0420 can be misleading. Try Loosening the gas cap and re-tighten the gas cap again. drive around for a bit and see if the lights go away.

A code P0420 may mean that one or more of the following has happened:
Leaded fuel was used where unleaded was called for
A damaged or failed oxygen sensor (HO2S) Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe Retarded spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings
Leaking fuel injector or high fuel pressure
Cylinder misfire
Oil contamination

 

An exhaust leak is the most frequent cause of P0420 and P0430 codes in the Lexus IS.

Usually small holes form in the mid pipe under the heat shield.

The cel comes on due to the fact that hot exhaust gases are leaking out, increasing the amount of time it takes for catalyst light off. The catalyst efficiency test is performed very early in the drive cycle, so it is hit-or-miss whether the test is performed before or after converter lightoff. That's why at the beginning of this problem, people find that the check engine light goes off by itself after a few days, only to return a short time later

 

Thanks guys. the gas cap is on properly, always to 1 click. I only put in premium gas. I think it is an exhaust problem like you guys mentioned. When I do press gas, it does feel like there's "air leak". I don't know if that's because of exhaust leak or a separate problem