Hi I was just wondering if any of you STS guys started throwing any P0420 codes (Catalyst System Efficiency below Threshold (Bank 1))? Could this be a bad rear O2 sensor or does it actually mean the cats bad? I live in an area that requires emissions testing (Visual/emission) so I need my cats. Is it possible to turn off what ever is senses the low efficiency with hp tuners right? now I have just been clearing the code once a week. Any help would be appreciated

- Tyler

 

use an infared temp gun- measure the inlet temp- coming from the exhaust manifold side- about an inch away from the cat- then measure the outlet temp of the cat- there should be a good increase in temp coming from the outlet. if the temp doesnt change- the cats trashed

thats really the only test you can do without a gas analyzer

if there is a good temp increase coming out- then change the rear o2 sensor on that bank.

 

I kept getting that code after i installed my rear mount turbo.. went away after about 2 weeks and haven't had it since.