my 98 A4 1.8T sat for about 3 weeks with a dead battery, didn't have the time to fix it. 100 hour weeks will do that to ya.. I put a new battery in it a few days ago and now i get the P1545 code and the car runs awful..I cleaned the throttle body out with some throttle body cleaner on the suggestions here, but that didn't solve it.. what do i do now?

 

I just got this issue today. Car is running super rough. Any solution? The battery was dead for a week.

 

For starters I would try doing a throttle body alignment. On newer cars, you can accomplish this by leaving the key in the "On" position for about 5 minutes. You'll hear a high pitched whine coming from the area of the throttle body. You can also do this using Vag-Com if you have access to one.

 

A throttle body alignment using VAG-COM fixed the issue:
Ross-Tech: VAG-COM: Throttle Body Alignment

The turn key in ignition for ~3 minutes but don't start car method did not work.