Right, after the change of the 02 sensor in the headers, I cleared the code and had no codes for a few days. I then had a CEL, and the PSI3 showed there was no current code stored but the historic code was P0175,' Bank 2 Sysyem too rich'. I think I have a slight blow on the headers which may be causing the issue, but my main question is where is the bank 2 monitored?

There isnt much Impreza related P0175 feedback on the net, so any help would be well appreciated.

 

Bank 2 is the LH bank but I believe that is irrelevant as I don't think youv got enough O2 sensors on your car to differentiate. Probably just a generic OBD description. Start by getting an emissions test done to see if it is rich.

 

I have 2 sensors so it seems, one in the headers which i just replaced, and one in the second cat after the downpipe. ~Ill have to get it looked at, cheers.

 

Bank 1 is the first sensor. Bank 2 the second. A blow may cause a problem. As its historic id wait a while. When no1 sensor failed the car probably ran rich leading to sensor 2 showing too rich

 

Yeah, I was showing a P0172 Bank 1 Rich CEL with the goosed front sensor. Sensor changed out and it went, to be replaced a few days after by this CEL. I can only think, as the headers had to come off to replace the sensor (long story!) I have an air leak in there somewhere. I can hear a bit of a blow there somewhere at high revs. Time to get back under and tighten up again. Thanks mate!