[MegaRam08]

Engine light has been coming on and then off ever 3rd drive cycle after the codes be present. It is a random occurrence and doesn't happen back to back.

The code: P0420 cat. System efficiency bank 1. Happens either freeway or city drive, but always around 1600-1900 RPM no change in drivability or anything noticeable at least.

Seeing if anyone else has had it happen and what they found to the cause or correction !?!

 

[ChiTownHemi]

This can happen for a few reasons. It happened to me because I have high flow cats, and if you have them too, this is the issue. If not, you may have a bad 02 sensor on the driver's side, or a worn out cat.

 

[MegaRam08]

Yeah I just bought the truck about 5 months ago. I do not believe there is anything aftermarket besides the wheel/tire package that come with the truck. And the 02 sensors is what I was thing because I wasn't sure if the code was pre or post cat. Just stated bank 1.

 

[ItsMike]

Any updates on this? I know this is an older post..

I am gettng the same code on my 2011 hemi..

 

[GTyankee]

read this & look at possible Causes

https://www.obd-codes.com/p0420