A good first start and inexpensive start is to test the brake light switch by starting the car and pressing down the brake gently, get some one to see if the brake lights are on. If they are on then from that point press the brake down fully...do the brake lights turn off when brake pedal is fully depressed??

If so you have a faulty brake light switch just change it and the BAS/ESP will disappear problem solved!!

I did this recently with 100% resolution.