BMW Repair: 83 BMW 320i O2 sensor, 1983 bmw 320i, unit lambda

Question
I have a 1983 BMW 320i and recently the "Oxygen Sensor" light on the passenger side of the dash has come on and now always stays on.  Yesterday I replaced the oxygen sensor but the light is still on.  I looked through a repair manual and I see that there are other pieces in this system, such as a lambda control unit, lambda relay, etc.  My question is:  how do I know which part is the bad one to get the light to go off and to make my engine run smoothly again?  Thanks.

Answer
" Follow your speedometer cable from the speedometer thru thre firewall, You will see that it terminates into a box...then continues on to the transmission .. the box is a mileage counter that reminds you to change your O2 sensor.....Change your O2 sensor...and or press a recessed button (with the erasser end of a pencil) this will reset your mileage on the O2 sensor...The Light will go out." -Roadfly.com  

Your car may be running poorly from something else.  Realize also these cars have a tendency to run poorly when they are low on oil or are in need of a valve adjustment.  let me know what the conditions of it running poorly are and we can diagnose it from there.
-cheers