A6 Jesse

with the factory O2 sensor. It was happening before it was replaced and now again after. I have an APEXi Turbo Timer connected to the O2 sensor line but it has been connected for 8 months w/o problems. Any ideas?

4Driver4

I'd start with the obvious: disconnect the turbo timer.

paulroad

that are measured in MILI-VOLTS. For 8 months the Turbo Timer was using the voltage but not quite enough for a code. Perhaps over time.. it is now interfeering. It is the best place and easiest place to start.

urq20vt

Audi turbo cars have coolant pumps that circulate coolant through the engine and turbos to cool them down when the engine is off and hot. In some ways, this is better than even a turbo timer. While the turbo timer won't hurt, it really isn't doing much for you. These are most useful on cars that were not turbos to begin with, and/or cars without water cooled turbos. Not meaning to rip on you, as it is good to want to protect the turbos, but sometimes the poison is less deadly than the cure.

First off, I would definitely find a different place to get voltage for the turbo timer. Seeing that the O2 heaters are switched on and off by the ECU (which also monitors those signals), tapping into those wires can definitely cause the ECU to think something is wrong with the circuit.
Also, how is it tapped in? A wire tap, like a Scotchlock? These are a bad choice, as they often damage the wires that you are tapping into.