abs light on

hi all, my octavia vrs has abs light on, traction light and brake warning light flashing, also my brake lights didnt work. this all happend when i put a new battery on it, (im a mechanic so yes it was fitted correctly lol) so where i work we are a VW dealer aswell as DAF trucks where i work, i asked one of the VW lads to plug there diagnostic computer on it and it brought abs pump module failure, and brake switch fault, played around with the switch and the brake lights are now working but stil got this abs fault, cant see how putting a battery on could spike the abs ecu as this is what it sounds like.........any one shed any light on this.....cheers