I have a 1995 850 Turbo Wagon with a little over 200,000 miles on it. Last August after a fill up my "Check Engine" light came on and stayed on.
I checked all the fluid levels and everything was fine, the car ran just fine. A couple of months later I took the car to Advance Auto Parts for a free scan,(even though my car is 1995, it has the OBDII plug under the coin holder.)
The scan showed code #:PO133, O2 sensor. the strange thing is that the car does not have any of the symptoms a bad sensor is suppose to cause. It runs great, I am getting good milage and the plugs look good.
Last week I got a Launch scanner from Harbor Freight, plugged it in, followed the instructions and the scanner showed no codes, just a couple of dashes followed by the word LAUNCH. After four scans the check engine light went out but came back on after about a 150 miles. I of course re-scanned until the light went out again, the scanner still showing no codes.
My question is, will the check engine light keep coming back on every 150 miles or so and do I need to worry about the O2 sensor?

Sorry about the long post, Peter