I like to disconnect the wire and then thread a box-end wrench over the wire all the way down to the sensor. I don't recall the size, but it is standardized and might even be an SAE size.

Personally I don't like adding a splice to the line, so I always use a direct fit replacment by Bosch, NGK or Denso.

John

The front sensor affects driveability. It gives data to the ECM and it in turn adjusts fuel and iginition mapping. The amount of the effect will depend on how bad the senor is.

DEWFPO
--
1998 S90 077,400 and 1995 964 154,100

If it is dead, it will affect your mileage. They really aren't that hard to put in-- use an 02 sensor wrench for best results-- some stores will even loan you the tool to do it yourself-- you'll need a 1/2 drive ratchet or a breaker bar too. Alternatively you can pick up your own tool for about $10. I use Bosch sensors for 90's Fords (like the 13913 or similar). You can just cut off the plug and crimp the three wires onto the original Volvo harness. My last one was $37 and it works great.

Good luck!