Oxygen Sensors Short-lived!
 

'96 SVX:
For the last 3 years, I have experienced several oxygen sensor failures, both front and rear. First, the rear sensor had to be replaced twice within 8 months and 1200 miles. (I am retired and annual mileage on this car is very low absent business use!) 1 year and 800 miles later, a front sensor went. 100 miles later, the wiring harness to an oxygen sensor (I don't know which) had to be replaced. 22 months and 1000 miles after the 2nd rear sensor was replaced, it triggered the CEL again. The dealer cleared the code, and 200 miles later, it did it again. The dealer - usually reliable - can find no reason despite checking with Subaru. Any ideas? (And no, I am not inclined to replace them myself.) :confused:

off the top of my head....
 

bad fuel, or bad install. Typically what I see on a semi-regular basis, is improper installation. The sensor is best installed with an anti-seize compound on the threads. Its common to buy an O2 sensor and find the compound already lightly applied to the threads with a protective cap over it. If ANY of that compound gets on the sensor dome it will contaminate it and cause pre-mature failure/inaccurate responses.

I'm assuming that the dealer is using genuine Subaru parts. You may want to inquire about this though. Aftermarket O2 sensors, and Subies generally don't get along.

If they are genuine Subie parts, you may have a failing catalytic converter. This will throw a #3 (downstream) O2 sensor code.

My words aren't gospel, just some food for thought.;)

Thank you for the quick responses. I will check out your possibilities! :)