p0420 caused by exhaust leak?

[99sho-time]

k guys threw a p0420 I have all new 02 sensors was wondering before i get into a plan to fix. this I have an exhaust leak and was wonder could that trigger it? it's leader at the headers and I need exhaust studs.

 

[stephen newberg]

If the leak is upstream of the sensor, it seems to me it could be possible.

pax, smn

 

[SHOMEX]

I will say yes, an exhaust leak like the one you described will thrown a p0420 or p0430 code depending on which bank the leak is; the most common cause of a cat low efficiency code its upstream o2 sensors or exhaust leak from the exhaust manifolds.