2008 Subaru Impreza 2.5i Sedan stock, 113k miles

Codes: p2096, p0137

My exhaust was leaking at multiple points. After I got this fixed, the codes came back after a few days. When cleared, the CEL will illuminate after a few mins driving on the highway.

I believe that the Upstream AF sensor has a rich bias. About 5 minutes after the car warms up, it produces a consistent negative current (-0.05-0 mA). Its voltage is 2.1-2.2 V. In that time the LTFT drops from 0 to -4%.

The downstream O2 sensor provides reasonable values at first, in the 1.2-0.4 V range. However this gradually drops to 0.01-0.02 V.

The MAF sensor appears to be responsive, increasing with engine RPM.
2 g/s at idle, 10 g/s at 3000RPM.

I dont hear any vac leak whistles while the engine is being revved with the hood up.

Any ideas?

2007 Impreza 2.5i Wagon, stock, 136k miles

Code: P0171 System Too Lean (Bank 1)

Taking a look at this in a bit. Either dirty MAF or serious vacuum leak. Built a DIY smoke tester out of a soldering iron and a pickle jar. Will update when I clear the code.

Here's one for you. I'm posting in this not because of a code. But the lack there of.

I'm the third owner of my 08 wrx. It has 155k miles. I bought it at 100k. Timing belt was done by PO at 90K. Paperwork to prove it was done. It was after my idler pulley exploded that I realized only belt and tensioner pulley were replaced. So I'm here about the lack of P0340 0345 codes. I have the timing belt cover off and found the issue.

Might I be the luckiest man in the world and just need to replace broken cog pulley check timing and replace timing belt water pump and compression test?

Thoughts?

Any idea what to look for when trying to fix that CEL. T
Thanks in advance.

This reply is for the general good.I expect most here are aware, but I just retaught myself this handy trick. When trying to determine my CEL reason, codes, etc., and what to fix first I noticed that my positive battery terminal was very corroded when I disconnected it. After cleaning the terminal and reconnecting it I noticed that the CEL was off. This was several weeks and over 500 miles ago. Codes are cleared, no CEL. Hope this helps others before they spend hundreds on parts they m ay not even need.

I have an 08 sti hatch with no sensor activity after looking under the car I found the sensor out of the exhaust, stripped, I managed to place it back in but now the car stutters under load and runs extremely rich, any help is greatly appreciated