Bad O2 Sensor

[nookatee]

Hello,
this question is actually on behalf of my friend's VW Beetle. Her O2 sensor has failed according to her check engine light code. The problem is: she has 2 O2 sensors, one before the catalytic converter, one after. How do you determine which one is failing? is there a way to use a voltmeter? I need some in depth instructions if that's the case because I SUCK when it comes to electrical stuff. Thanks

[jrhaile]

umm go to a vw website man. sorry

[nookatee]

nobody knows how to determine which O2 sensor is bad? I mean...this isn't a VW question, it's a O2 sensor question. I think our E36's only have one between the headers and the cat conv. but...the fact that it's on a VW is totally besides the point.

[93 325i]

My money is on the O2 sensor before the cat. Don't know how to be sure tho.

[jrhaile]

usually by looking at the sensor itself.. if it's black and gross, then it needs to be changed.

[triggrhaapi]

the check engine code should tell you. get an OBDII reader.