The Subaru CEL thread

[kscoob]

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?