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Old 12-09-2012, 07:57 PM   #9
Scooby Newbie
Member#: 322645
Join Date: Jun 2012
2012 WRX


Originally Posted by RoadKillDMD View Post
Your rear o2 is there to monitor the cats efficiency. It won't really affect your tune, except you will get a CEL showing a rear o2 error that needs to be tuned out. The FRONT o2 sensor located in the up-pipe is what is actually reading AFRs for the cars ECU.

Don't replace anything. Just ADD a wideband for monitoring purposes.

Again, your o2 sensor is probably fine. Don't replace anything. The wideband gets its voltage from the car, but not the readings. The readings are 'real time' and can be logged with a piggyback ECU, but not the stock ECU (afaik).
Ok so the wideband would be to just monitor. What is it about the stock narrowband that prevents that from being used to monitor like in the log i posted above? Is the A/F data collected from it incorrect? Just want to know if the A/F i logged is valid or not. Either way I would like to get a wideband.

I read that the rear 02 on newer subarus does affect closed loop A/F but I guess that was misinformation or i wasn't understanding it correctly. Sorry if this all comes across as noobish but I am trying to take a crash course in the fueling and engine managment systems of the WRX while studying for finals.

I am popping a p2097 post catalytic system too rich code. That's triggered by the rear 02 correct?

So if it is not the 02 what else in the fuel system or ECU would trigger the car to behave like in the logs above? FPR?
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