o2 sensor problem

[dabomba]

Just had to recently get a new turbo back full exhaust thanks to my exhuast being damaged on 3 different spots (downpipe, cat, and rear exhaust pipe by the axle) and all of them had holes. They all had pretty bad exhaust leaks and you could see how bad it was when the car was on. i have a 98 eclipse gs-t and they took out the cat. they made a new bunghole also for the o2 sensor and carefully took it out and put it back in the new bunghole they made. cel came on after about a day with the new exhaust and it came with the fuel trim code p0170 or faulty o2 sensor is likely the cause. my gas mileage has went from ~24mpg all the way to around ~19mpg. i know its either the back sensor was toasted from the heat, or its not reading correctly because of no cat being there. Its obviously dumping in to much fuel and you can smell it out the exhaust. Is there any ways to test the rear o2 sensor? cause it was replaced about 2 years ago... Also if it is working good but can it be thrown off because the cat is eliminated so its telling the ecu to dump a lot more fuel in? and is there a mod that for sure works so the code can go off or at LEAST improve my mpg back to where it was at previously. Also is the second o2 sensor's only job is to read if the cat is working properly while the front o2 has the brunt of the work or what? thanks for any helps guys. I get one problem after another with this car and has been doing so since it was rebuilt three years ago..

 

[everydaydriven]

My personal experience, is when I swapped my exhaust out for my 3", I unplugged the rear o2 sensor an. Left it unplugged. Haven't had a cel yet! I also have the front o2 simulated through dsm link!

 

[lilsam]

the o2 sensor that does the rich/ lean out the car is the front o2 because you have a 2g you have 2 the back is pretty much usless because all it does its check the efficiency of your cat. so i would this you have a front o2 senor problem not a rear

 

[dabomba]

yea i meant to say front o2 sensor. . cause its hrowing two codes. p0170 and p0456. the second is a emissions evap leak and first one is bank 1 o2 sensor failing. Just weird that front o2 sensor was fine before exhaust install then took a crap after new exhaust was put on.. gonna replace front o2 and erase the codes to see what happens!!