Got a 1999 A4 2.8 with throttle body issues. Purchased with rough running, fluctuating idle, etc. PO said he was told throttle body needed to be replaced. After cleaning the throttle body I purchased Vag-com lite and tried a TBA. It gave me an error code when trying the adaptation.
Purchased a new throttle body off ebay, matched up perfectly, installed it, exact same issue. Still idles horribly, no power, runs rough.

Codes
18010- Power supply terminal 30: Voltage too Low
P1602 – 35-00 - -
17953- Throttle Valve Controller: Malfunction
P1545 – 35-00 - -

Any ideas out there??

 

Damage to the wiring maybe? The low voltage code can be ignored most of the time. I'm wondering whether you have a broken or shorting wire in the harness to the throttle body. Also, have you looked into a clogged EGR or PCV system or a vacuum leak?

 

I haven't looked into clogged EGR, PCV or vacuum leaks. I figured the code was a straightforward throttle body problem.
Prior to replacing the throttle body, I did locate a loose primary 02 sensor with damaged threads that I replaced.
I'll try to check those items suggested, can they also give the throttle body code I'm seeing?