My brake wear indicator was on, I took it to Mercedes and they said the front brake pads and rotors needed to be changed so I ordered a set and did it my self as well as replaced the sensor. The pads on the ml500 looked like they were still new anyways I changed everything and drove truck about 30kms and the light is still on.

How do you reset the light and is there just one sensor on a 06 ml500 or does the rear brakes have one as well?

 

could be the rear pads? there is a sensor there to. theres a common problem with the brake wear sensor harness breaking at the rear right. follow the brake wear sensor harness from the rear caliper and follow it and it plugs into the body harness and the wire is usually broken right where the 2 harness connect right behind the connector.
just recheck all your work