Just wanting to confirm some info I was told, i have a full exhaust on an 07 suburban with no cats and im running defoulers in my downstream 02's and was wondering if this will effect it when I start tuning the truck? Someone told me that if I don't have cats then I don't need my downstream 02 sensors and that it won't effect the way the truck runs is this correct?
thanks in advance

 

I've never heard of defoulers

For tuning you only need the upstream O2s

 

Defoulers are use to prevent engine light from coming on when you delete the cats and ok thank you for confirming it for me

 

And I just realized the way I worded my question probably wasn't right, I meant after I tune MAP and SD and then put all the settings back in place will the defoulers effect the tune and would I be better off running the o2's without the defoulers?
sorry about that

 

Some computers need to have the cat test disabled if you remove the cats and the rear o2 sensors.

I'd have to look at the file to confirm if yours needed that. But you'd need HP Tuners for me to see it.

I have a 2007 Yukon Denali tune on my computer and there is Post o2 sensor test as well as a Cat Test on that file, both of those would need/want to be turned off. Not disabling them would run the diag test on and off while you drive, could also reduce fuel milage a tiny bit and make tuning more of a hassle if they were not shut off first.

 

Everything to do with the cats are turned off, I just got hptuners a few weeks ago and was getting ready to start tuning the MAP and SD to get familiar with everything but I just wasn't sure if I should take the defoulers off and keep the downstreams active or failed after the whole turning process is done

 

The ONLY thing downstream O2 sensors can do is illuminate the MIL light.
If you have disabled the MIL function, then the downstream O2 sensors are just plugging up holes, and drawing a little bit of heater current. " You don't need 'em "

 

Not entirely true, not having rear o2 sensors on a truck that uses them for diagnostic tests can make the engine do more than just report the check engine light.

Even on many P59 controllers, if the circuits are left open on the rear o2 sensors the cat test will always run. If you leave them plugged in, the test won't run.

 

I know on my e38 it has a disable setting and I do still get the heated test readiness when you scan