'tuning out the cats' question

[crawlinss]

well, i got my truck back today, had bad cats, and took it to a friend of a friend at the dealer, and he 'tuned out the cats'. i needed my truck back ASAP, he told me it would pass emissions. (illinois is just a generic obdII scan). now im asking for a detailed answer as to HOW this is done exactly. i understand the part about still running the 02 heater self check and everything, but if the pcm is ignoring the rear 02, how does it ever get into closed loop? im going to text him in the morning, im VERY happy with the results so far, the truck feels like its come back to life. anyone in chicago needing performance work done get a hold of me and ill put you in contact, he works at a dealer, but has done a lot of high end upgrades on ssr's zo6's etc etc. anyway, just looking for a more detailed answer if anyone has one. thanks!!

[Cramer]

I don't really understand what was done. If it had bad cats, then they would have to be removed or replaced with new cats. If the cats were gutted or removed and the guy tuned out the rear (downstream) sensors then you should be good to go if the scan shows all the system readiness tests are OK. The downstream sensors are basically a secondary meter that gauges the emissions that have passed through the converter.

 

Sent from my Motorola RAZR MAXX using Tapatalk 2

 

 

[2003_SuperSport]

I don't really understand how you felt a big difference in him tunning out the cats, unless he replaced the bad cats or gutted them and even then having cats and no cats are hardly noticable in an upgrade unless they were indeed bad and throwing codes causing the PCM to pull timing thus performance... And its not necessarily tunning out cats rather than tunning the PCM to read the rear ones as running perfect all the time thus passing emissions test or OBD2 tests...

[BLNAWAY]

I don't really understand what was done. If it had bad cats, then they would have to be removed or replaced with new cats. If the cats were gutted or removed and the guy tuned out the rear (downstream) sensors then you should be good to go if the scan shows all the system readiness tests are OK. The downstream sensors are basically a secondary meter that gauges the emissions that have passed through the converter. Sent from my Motorola RAZR MAXX using Tapatalk 2

he has another thread(see below) where he talked about his issue with the cats, he took it and had the cats cut out and had straight pipe installed, in this thread/post i think hes looking for the technical way of how someone goes about tuning out the cats? but i could be reading wrong, i dont kno the procedure so i cant have any helpful input

 

 

 

http://www.silveradoss.com/forums/topic/83701-ss-having-engine-troubles-need-help/page-2?do=findComment&comment=932634

Edited November 22, 2013 by BLNAWAY (see edit history)

[sprayed99]

he has another thread(see below) where he talked about his issue with the cats, he took it and had the cats cut out and had straight pipe installed, in this thread/post i think hes looking for the technical way of how someone goes about tuning out the cats? but i could be reading wrong, i dont kno the procedure so i cant have any helpful input

 

 

 

http://www.silveradoss.com/forums/topic/83701-ss-having-engine-troubles-need-help/page-2?do=findComment&comment=932634

Depends on your definition of "tuning out cats"

 

Some just disable the MIL where it wont through a code or set the SES light for the codes related to the down stream O2 sensors. Personally this isn't all you should do, but hey some people don't know any better and some tuners eat that up when they make a quick buck by spending 5 minutes Disabling DTCs