BAS/ESP warning light c200 w202 yr2000

any idea what might be causing the BAS/ESP warning light to be permanantly on ?
The brake pad and discs are in good condition.
What sensors are involved with the detection of a fault and what are the main culprits?
Cheers.

Change your brake light switch

Thanks I'ii try it!

Thanks Simba, resetting the brake switch has got rid of the warning light but I still don't get Cruise Control or Brake Assist, Any ideas please

Cheers