It won't be if it has a supply voltage too low error. It's either wiring or ECU.
There are used ECU's on Ebay which you can code in easily. Around £100 max or speak to A8 parts.
http://cgi.ebay.co.uk/Breaking-Audi-...item415596ed7f
Check the part number for yours particularly the last letter and you should be fine.
Supply Voltage errors is usually ECU errors. The Terminal 30 is Audi speak for (If I remember correctly!!!) ground. If you let me know your email I can send over the PDF's for it and you can check all terminal 30's on the ECU and pump?