P2097 Post Cat Fuel Trim Sys Too rich B1... 2005 Forester

[Sapper 157]

Hey all. Its been awhile. 

Got a 2005 Subaru Forester XS with the SOHC EJ25 N/A. Since around March, I've had a code P2097 off and on, and within the past month it has become a constant code. So far I have replaced the downstream O2 sensor (Denso replacement), the air filter, and the front A/F sensor was replaced with OEM only 11,000 miles ago so I am very hesitant to replace that one again. My short term fuel trim hangs around -2% to +3 on the highway, and long term trim stays around +4.7%. I have been told that those numbers are "normal" but please educate me if that is not true. My MPG is 23 - 24, and the car sees a mixture of city and short term hwy driving... so i believe that is a pretty average fuel econ. Is it possible my ECM needs to be reprogrammed? 

Other Information: 

• Car idles smooth as silk at around 650 - 670 RPM
• Car starts great 
• Engine response feels peppy (as peppy as a 4EAT can be)
• Car does burn some oil (quart every 1200 - 1500)
• Does not have any obvious fuel leaks at the injectors, fuel pressure regulator, etc. 
• I do run some MMO thru it every other fill up

The following was also replaced around 12,000 miles ago:

• Head gaskets (OEM)
• Spark plug wires (NGK)
• Spark plugs (NGK)

I have not done any fuel pressure or cat back pressure tests, would those be good to do? 

Thank you all for any insight. 

[GeneralDisorder]

Sounds like you have two choices - OEM Subaru converter, or flash the ECU and delete that code and the post cat trim system. A Tactrix cable and ECU flash is cheaper than a cat and also a lot more sure of a fix. While you're in there you can delete the cat codes, and secondary O2 codes, and anything else you never want to buy again simply due to government mandate. 

GD

[Sapper 157]

Update: I decided before I tried the Tactix cable, I would just see if throwing a new A/F ratio sensor in would do anything. So, after installing a new Denso P/N 234-9122, my light has not come on for 92 miles now. So it appears that my front o2 sensor went bad early for some strange reason