I recently installed ARH and a catted y this weekend. Before the install I read nearly everywhere that the rear O2's would have to be tuned out/use simulators. However, the y pipe had ports and my stock rear O2 sensors plugged rite up to the stock locations. No SES for two days until tonight. Does the increased flow or heat simply kill the rear O2 sensors over a short time? Tuning them out will not be a problem I'm just looking for clarification as to why rear O2's cannot be run despite the presence of ports in the catted y.

 

With a catted Y there should be no reason to tune out the rears. They are meant for making sure the cats are doing their job. The fact that yours are throwing problems isn't normal. What codes are you getting?

 

Not sure, I'm going to try and have it scanned tomorrow. So rear O2s are supposed to be used with longtubes and catted y setups?!

 

I've never heard of them not being able to be used on similar set-ups as yours which leads me to think there is some underlying cause as to why yours seem to be causing problems. Find out the code at a local auto parts store and let us know as that will help a lot in getting you in the right direction.

 

I have heard of guys having issues with the aftermarket cats still setting off you MIL. They are still quite a bit smaller than the factroy cats. Most guys still get the rear o2's tuned out. Most tuners just turn that stuff off, kind of like second nature.

 

Ya I did a little more research and it looks like high flow cats throw codes usually. I'm still gonna get it scanned but i have a feeling this is the issue.

 

Agreed, even with high-flow cats you usually have to tune out the rear o2 codes!

 

I left mine in for appearances sake & just had them tuned out. They make great plugs....... its almost like they were really supposed to be there!!