low brake pad light on dash won't go off. on 2006 Mercedes-Benz R350

Replaced the front and rear pads and rotors on a 2006 mercedes r350. after about 2 miles brake light on center counsel came on and won't go off. Checked sensor it was installed properly. Checked and found 5 volts power going to rear sensor and was told there should be none. Is this true and if so what parts and procedures are required to fix this problem.

Asked by for the 2006 Mercedes-Benz R350
did u repl the sensors?