Hello Everyone,

Thank you for your help. Between your advice and the pictures and text from Bay 13 I was able to successfully replace the front O2 sensor. I want to share some advice. After you install the new O2 sensor, you have to disconnect the battery for 10 to 15 minutes and then reconnect it. If you don't the Check Engine Light will remain on. I didn't the first time I started the engine. The Check Engine Light remained on and I thought I had failed. Of course, make sure you have the security code handy for your radio to be able to re-program it. When I disconneted the battery cable, waited 10 to 15 minutes and then reconnected the cable and started the car, the CEL went off.

Separately, I had an odd experience which I would welcome comments to. Based upon the pictures from Bay 13 both wire couplings for each O2 sensor (front & rear) are supposed to slide onto a metal bracket attached to the housing of the transmission which secures them. The bracket on my 850 (with a manual transmission) was missing. I went to my local Volvo dealer and confirmed such a bracket should have been on the car. I order one together with the screw you need to secure the bracket. I installed the bracket and put both O2 couplings on the bracket. It was a very tight fit for the front O2 sensor, there was barely enough slack in the cord to slip the coupling on the bracket. I suspect the bracket was removed on this car when the transmission was replaced under warranty by the prior owner. I suspected the technician when he put the transmission back in, didn't bother to re-install the bracket.

I then checked my other 1996 850 wagon, also with a manual transmission. It too was missing the bracket that both O2 couplings are supposed to slide on to. I was surprised, because I had purchased this car new and the transmission has never been replaced, though of course the O2 sensors have been over the years.

I asked my mechanic who worked in a Volvo dealership throughout the 90s and early 2000 when the 850 and subsequent V70 were introduced. He confirmed that these cars, even those with manual transmissions, all came with a bracket where you were to slide the O2 wire couplings on. My other '96 has the two O2 cables secured with wire fastners, so they are out of harms way and will not chafe against any surface. Still I'm surprised that both cars are missing the same bracket, which according to Volvo they should have. My mechanic did say the early O2 sensors failed alot and it was common when removing the couplings off the bracket that secured them, they would break. Fortunately it was the part of the cord that was being replaced when you install the new O2 sensor. Still, I would like to hear the experience of others. I have to confess putting the couplings on this bracket is challenging.

Thanks again to all for your help.

Hugh