Vsc And Ebd Lights Up At The Same Time.

[EMDG]

My 2001 RX300 recently started showing the VSC and EBD lights together. I purchased an OBD reader which showed the code reading of P0420.Tis indicated 'Cat below threshold Bank 1'. I found that a sensor in front of the cat had detached from its mounting and was hanging loose, a simple job to bolt it back again. I canceled the code to extinguish the warning lights. A month later they are back again. Two questions, why does the VSC light come on and what faults could bring the EBD light on again?