One problem related to air brake antilock control unit/module has been reported for the 2001 Audi A4. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2001 Audi A4 based on all problems reported for the 2001 A4.
Failure of abs controller in 2001 Audi A4 1. 8t. Was told by dealer that engine heat melts soldering in unit. $1,300 estimated repair ($1,000 for part alone). Intermittent failure light and beep when driving, abs not active when light is blinking. I've read on Audi websites that this is a common failure that Audi of America refuses to take steps to rectify either monetarily or through redesign of the controller to prevent future failures.