AudiS4guy - NorCal

I was under the impression that both were heater circuit wires. Someone just told me that they are not interchangeable...one was signal (i thought black was o2 signal feed to the ecu???) and the other was for the heater circuit?? TIA =)

My2ndS4

ones and I haven't had any problems.

ryans4

i didn't pay attention when I spliced my VW O2 in, of course, you have a 50/50 chance...

AudiS4guy - NorCal

yeah...but you could have been lucky and got the right ones connected =)...50/50

quickaudi:STFA

For 3 wire O2 sensors, they are interchangeable. They are just a heated wire circuit.

AudiS4guy - NorCal

so would that apply for the 4 wire o2 sensors as well?

P. Bauer

just mark them before you cut and then trace the wires up to the plug.

quickaudi:STFA

Would think so. 4 wire sensors use two white wires, a black one, and a gray one.