johnnyb438 Posted April 21, 2014 Share Posted April 21, 2014 Was driving and this happened to me. Mods are Stage 2 with an Invidia catless downpipe, and a Cobb AP. My filters and injectors are clean, we're actually replaced. Does anyone think it could be the up pipe that has gone bad and time to go full catless? Has been on Stage 2 for about 19k miles and was clear of codes until recently Link to comment Share on other sites More sharing options...
notthesnail Posted April 22, 2014 Share Posted April 22, 2014 You got a 420 code on 4-20? Was your car smoking? I choose personally to drive a car with one cat in it, but it's not in the up-pipe. Removing the last cat probably isn't going to get rid of the code. If you're getting this code with new injectors, then you're probably getting more fuel. Consider a pro tune. Link to comment Share on other sites More sharing options...
Max Capacity Posted April 22, 2014 Share Posted April 22, 2014 Front O2 sensor, replace it with a OEM one. they seem to last longer. Easy item to replace if you have a O2 socket and a screw type clamp around it to keep it from spreading. http://legacygt.com/forums/showthread.php/trouble-codes-cels-26113.html Bank2 is the rear sensor, any after market one is fine there. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
subiestang Posted April 23, 2014 Share Posted April 23, 2014 P0420 is a cat efficiency fault. You have no cat. You need to program accordingly. Link to comment Share on other sites More sharing options...
johnnyb438 Posted April 26, 2014 Author Share Posted April 26, 2014 Thanks for the help everyone, come to find out as I was inspecting the car I put a new 02 sensor on and it still came on. No the car was not smoking, however I have had the car on 'fuel economy mode' when this happened. I did some research and have read that if I reflashed it to Stage 2 it would rid the code, well it did. I daily drive this car approximately 120 miles every other day, so it's been nothing to amazing to me, thus the reason why I had it on economy mode. But can anyone explain to me why the light came on because of the economy mode? Maybe the vehicle has been noticing that it wasn't on Stage 2 for quite some time and triggered the ecu. I have been driving the car since I reflashed it for at least 300 miles now and no codes, and she still pulls Link to comment Share on other sites More sharing options...
ScoobyGT15 Posted April 26, 2014 Share Posted April 26, 2014 The economy tune (if im not mistaken) is for when the car has no mods basically stock. Since your running with a downpipe in the economy tune its throwing a code because that o2 sensor in the map is not set to read those emissions. Someone correct me if im wrong but i think thats it. The stage two clear the o2 monitors so that the cel doesnt come up when you start changing your up pipe and down pipe. Sorry if i am off. I don't use my ap anymore since my rebuild. We created my own tune and took care of the monitors through the software Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
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