It's a 2004 A6 3.0 220k. I was getting a CEL coding the B2 S1
Code:
17528 O2 Heating B2 S1 open circuit
P1120-004 No signal/communication

I replaced the O2 sensor and it throws the same code before I get to the end of the driveway!!!
It's a Bosch 17353, 5 wire (6 pin connector) not a universal 4 wire. I have found a million threads on how to check the 4 wire heater circuit with a DVM, but nothing on the 5 wire.
Can someone help with what leads to check the heater in the 5 wire sensor?
They are red, white, grey, black, and yellow.
It is my luck to get a "new bad" sensor and would be a lot easier to check it before replacing it AGAIN!!
If it isn't the sensor, where else can I look? The harness and plugs look good, no obvious damage.. It runs great, and haven't had any performance loss, just annoying.
Thanks