Hello All,

I have a 1996 850 GLT wagon with a 5 speed manual transmission. The “Check Engine Light” came on. Went to my local mechanic and with a scanner he confirmed the front O2 sensor was dead. I asked him if it was necessary to replace the rear sensor too, and he replied “No”. Not that I want to spend money needlessly, but I recall reading or being told it was a wise practice that when one sensor failed, it was more prudent to replace both O2 sensors (front and rear) rather than the one that failed. Any comments/suggestions?

Secondly, my mechanic “cleared” the “Check Engine Light” but recommend replacing the front O2 sensor. I have an O2 sensor socket, and for the first time will try to replace an O2 sensor on my own. Assuming the “CEL” remains off, after I install the new O2 sensor, should I still disconnect the battery cable to keep the CEL off or just install the new O2 sensor?

Also, any suggestions/tips regarding the replacement of the front O2 sensor I would welcome with appreciation. Thank you to all who reply.

Hugh