I think the O2 sensor is available from: http://www.fcpgroton.com/volvo.htm for
$170. I bought mine there.
'97 960 120k miles

I have an update on the 02 sensor. I bought the wrong 02 sensor. Alhough Bosch said the right part was 13119, it is the wrong one. This is a 3 wire 02, and the plug and one on the car is a 4 wire with a diffeent connector.

While the car us up, I read the number off the 02 on the car: 025 003 592.

Anybody have an idea how to be sure I get the right one, or have the right part number for the right 02 if the 025 003 592 is not correct??

Hope I can get a credit.

I used the following process when I replaced both O2 sensors on a 1997 960:

Drive the front of the car up on ramps; disconnect the battery, work on figuring out how to decouple the O2 sensor connector(s) on mine The was a metal loop fitting that I had to slide back; disconnect the connector(s); then remove the O2 cabling fasteners and cable clamps along the cable routing save the fittings; once the cable is free, using the crows foot special tool from Autozone, remove the sensor.

The sensor is pre-lubed so install the sensor, not too tight, the sensor has a crush washer; reroute the cables, connect the connector plugs; then clamp them and retie the cables down; reconnect the battery and reenter the radio code. reset the codes and give it a couple of days to see if it comes back.

With a new sensor if nothing else you have eliminated it as a failure component and have improved the response of the closed loop system.

If the codes come back, start looking for vacuum leaks between the air intake and the intake manifold. If you can reset the codes easily, you might try to isolate possible vacuum lines first by plugging the inlets and see if the code goes away or changes; then try the butane trick around the manifold. I have heard that WD-40 will also work but is messy.

Let us know how you make out.

The sensor is rt hand threaded.

Before you start the job, make sure that the new sensor will fit into the O2 sensor socket. I bought a cheap import on Ebay and had to shave some out of the ID in the socket to get the Bosch sensor to fit in.

It is preferable to get a socket with an external hex on the end, that way you can put a spanner on the hex to torque the sensor. There's not much clearance to the body/subframe and the spanner is easier than a ratchet.

Be aware that the O2 sensor is fragile. The external cylindrical shell cannot be dented or manhandled in any way or the sensor can be ruined. The sampling of the external air is thru that cylindrical case and any changing of it is going to affect the balance where lambda=1. You want to gently get it situated in the socket with the wires going out thru the back of the socket. Put a little bit of anti-seize on the threads of the nut but NOT on the nose of the sensor.

You must be careful not to cross-thread. It's at a weird angle, so it's hard to judge. Get the nut engaged in the cat internal threads as far as possible by hand turning the socket; only using the spanner AFTER that to apply torque.

You'll have to drop the exhaust down at the downpipe to get clearance so be prepared to deal with those potentially nasty oxidized flange nuts at the downpipe. I like to clean the studs first with a stainless steel 'toothbrush', then apply a bit of anti-seize to the stud threads & maybe a bit of spray penetrating oil to the nut above the anti-seize and THEN try to crack them loose. It's definitely no fun when any one of those four nuts misbehaves.

You'll have to gently remove the little plastic clips that clip the O2 sensor harness along the transmission and up on the oil dipstick bracket. That aged plastic has a way of breaking very easily.

Most of the trouble is dropping the exhaust down and also dealing with the plastic clips.

When you put the exhaust back up, get all the downpipe flange nuts on and almost, but not quite snug. Then jiggle/nuzzle the downpipe ends into the exhaust manifold as you snug the flange nuts to 'feel' where the best fit is. It helps to make sure that there are no leaks at that interface.

Have you checked for vacuum leaks or a bad intake gasket?

DanR '94 964 332,000 miles (98,000 on the new engine)
--
DanR

Normally the sensor's threads have anti-seize on them out of the box; if not, defintely put some on, but sparingly.

Brickster,
I have a 97 which is different (2 sensors), but I don't think you'll have any problems. Boards always warn about cross-threading the new sensor and ruining your cat, but it doesn't seem to be an issue with the bricks. Mine is stainless steel and solid as a rock.
I sprayed the old sensor with a little PB blaster the night before and they came out easily. I have to borrow a new type of wrench from autozone, because my old socket was too tall. The new type ("Crowsfoot") is only about an inch tall and I didn't have to lower the exhaust or even jack up the car... Of course, jack stands are your friend if you are going under the car.
Try to keep things clean and don't put anything on the threads or around the hole in the cat. You don't want to contaminate the sensor. It's hard to remember, but I think I got at least 2 full turns with my fingers before things started to snug. Don't just catch a 1/4 turn and start wrenching down.
Nice to have a half dozen little zip-ties to tiedown the cable using the same locations that the old cable used. I started taking out the old sensor at the connector (by the tranny stick) and then installed the new sensor and routed the cable in reverse back to the connection. Clear the codes and go.
I suggest you do a quick search for other threads, because there was some discussion about having to re-activate the emission logic that might apply to your '95. It should come to life after a few weeks once you hit the magic combination of driving; but, if you need to pass a state emissions test, you can force it...