What would be the general concensus about the O2 sensor on the Legacy ?
Fortunately the computer is sufficiently smart to detect a connected or disconnected O2 sensor, but not a lead fouled sensor. According to Subaru, the O2 sensor is not present to meet the pollution requirements, it is there to meet the fuel efficiency requirements. Apparently if the sensor is disconnected, the ECU reverts to an open loop mode which is slightly richer than the closed loop condition but by law it has to meet the pollution criteria in this condition. Subaru told me that I might even detect a power increase due to the richer mixture but I shouldn’t bank on it. This all sounds too good to be true so what is on the down side: Well it appears that the O2 sensor is also used to provide a back up system should other sensors fail i.e. the famous limp mode. If you remove the O2 sensor this mode may be limited. I have known about this for some time but my source did not sound too convincing basically he was saying this should happen, not that it actually happened. At Oshkosh this
