I had my car scanned at auto zone and codes 0300,0420,0452 came up one was rmm and the other was low catalyst,i do have a magnaflow high flow cat but it says its epa legal.Well my solution to this was going to be to get an intence pcm and get the rear 02 deleted but i dont think that will turn the other code off for rmm what causes that code can a faulty or not working 02 or say knock sensor trip that code?any opinion would be helpfull

the magna flow cats on 2000+ will usually set the engine light off the only after market one i know of that won't is a Goerlich 608227 or other goerlich models made by AP exhaust here is the link to the site i just put one on mine
http://performance-curve.com/3goerli...dii608227.aspx

I took it to auto zone to scan for the service stability system that code didnt come up the only dash lights i have on are antilock,traction control,and check gauges in my head up, that stuff has nothing to do with low catylist or rmm theirs no check engine just check gauges light,and of course the guy at auto zone was puzzled and told me to go to a garage for advice well you guys are my garage lol

Actually that link that you sent me sawgunner,i tryed to buy that same converter from that same site and they told me they would not ship to my address,i was puzzled and kinda mad so i bought a magnaflow from summit racing for 75 bucks,but i saw that u had one and tryed to buy it before i bought the magnaflow almost 2 months ago because you or sombody said it wouldnt trip my light off

huh no kidding i had the same issue try them on ebay the service stability could be a multitude of thing i just completed the last fix on mine on my 2000 i had a bad yaw sensor #1, a bad wheel speed sensor, a bad height sensor, and the steering wheel position sensor was gone (i have a write up on that one) https://www.gmforum.com/mechanical-134/replacing-steering-wheel-position-sensor-2000-a-287531/ this should help you if you have this bad in your car will do a write up on the other as well

That thread is really nice if i have to replace that its will help but is there any way i can narrow it down to that before i replace it. Because i have no trac control or abs is that leaning more towards wss or can the wheel position sensor trip that light on the dash to

i have only had those lights come on twice would assume a bad hub/ wheel speed sensor but mine was random what i did was took it to the dealer and had them check it for stability codes they charged me $90 but i had all the codes to look up and fix them most places i don't think can check for those codes unless the have a tech II scanner i will scan what i got from them into here as soon as i can find it again once you have the codes from your car check here https://www.gmforum.com/specifications-general-information-132/obd2-codes-meanings-278800/ and you can look them up