E49 the e49 code does exist, my car is a 1990 cadillac deville. Ive looked it up on another website. under the code it says AIR management system error. I have access to diagrams and things but im not a super mechanic so they dont really help much. I dont even really know where alot of the parts are. I have a replacement oxygen sensor but I dont know where the other one is to replace it. or even if thats the problem. im just so confused really. lol

Go to http://alldatadiy.com/ and buy a subscription for your vehicle. If you want to repair it yourself you will need this data. It is good for 1 year and has, testing and inspection guides, component locations, wiring digrams and a lot of info the DIY'er needs.  I am looking in all my code manuals and still do not see an e49. AIR is a system that puts fresh air into your exhaust so the emissions at the tailpipe are lower. It's an EPA mandated system. If you have to pass an emissions test in your state or county you will have to get them system woking properly. Check out alldata it is worth the 30.00.