: simple question

12-26-2008, 12:22 PM
One that I dont know..... code 1221....oxygen sensor..... which one is it... pre-cat or after the cat....sorry....92 525i

12-26-2008, 09:15 PM

, don't know if this will help you, but I replaced both and code went away...

I know, probably not what you wanted to hear. but if ya gonna replace one, might as well do both while yer under the car!

Also, have a good friend of mine who has a bitchin 94 LT4 vette who had a similar problem, ie .. codes flashing check engine etc, and the thing ran like crap... turns out, check this...

you CANNOT solder wire extensions onto a O2 sensor.....

apparently they are steel wire and the sensor itself uses the wires insulation as a heat dissapant to regulate the correct reading (voltage output) when the car is at temperature to provide the computer the correct reading for fuel/air mixture. He got a "splice kit" for the left side O2 sensor and viola!!!! the code went away....

I had never heard of anything like that, but when i researched it, I was amazed by that nugget of info!

anyway, good luck and happy holidays!!