The link between o2's and throttle body.

[judeisnotobscur]

I've been having a hell of a time tracking down an electrical issue. turns out that the o2 sensors and the throttle body run off the same 5v reference signal from the ecu. In some instances, bad o2 sensors can affect that reference signal causing the ecu to see faulty readings from the throttle body. This has even been known to fry ecu's.

after a phone call to ross-tech, I simply unplugged my o2 sensors and bam, throttle body came in on adaptation after a couple months, and 1 throttle body later of not doing so. I only unplugged the front o2's because i don't have any rears, but you would want to unplug all of them when diagnosing this issue.

I'd like to give a big shout out and thanks to Ross-Tech. The guys over there are top notch.

[Capt. Obvious]

The weirdest shit is interconnected on these cars!

[DiscoPotato]

S4s do some weird shit sometimes.

[NOTORIOUS VR]

Are you sure that the O2 sensors are running off of the 5V reference? It's been a while since I've looked at the schematics but I'm almost positive they don't, and that they're fed 12V and tied into either the injectors or coil power.

That the O2 sensors (if they're shorting/damaged) might cause other issues with the ECU because of back-feeding, that is entirely possible though.

[judeisnotobscur]

I didn't check the schematic again but that's what Ross tech said.
After unplugging the o2s the tb aligned right away... either way the o2s were causing the tb issue.

[AudiSportB5S4]

Great group of guys.. That's why I bought my first HEX-USB cable from them, and then recently just bought a HEX+CAN USB to do all VW/Audi's to date. Nothing beats the real thing and customer service

[NOTORIOUS VR]

I didn't check the schematic again but that's what Ross tech said.
After unplugging the o2s the tb aligned right away... either way the o2s were causing the tb issue.

Yeah going by every O2 sensor I've ever seen, they're always supplied 12VDC and not 5...

But since the driver and heater circuit inside the ECU is what controls the ramp of the heater and nernst cell(s) a short could cause any number of unpredictable issues

[034Motorsport]

While almost anything can cause shorts and weird behavior, the O2 sensors in our cars don't use a 5v reference; O2 sensors create their own voltage. Their heaters are 12v.

Sounds like you got something weird going on; I personally don't believe they are directly connected to eachother in anyway, but you perhaps were having a short due to crossed or cracked wires or something of that sorts.

Regardless, sounds like its getting fixed!

[megafreakindeth]

a dirty throttle body will throw off the fuel trims and set boost leak codes and lean/rich trim codes. its stupid weird but it does happen. if you clean the electrical portion of the tb and the motor it will magically go away. This usually happens on 1.8ts though but the throttle body internals are all the same so i guess it can happen to anyone.