Brake Antilock Wheel Speed Sensor problems of the 2009 Mitsubishi Lancer

I was driving highway speed when there was a weird noise and my abs light came on. I had to run an errand and when I got back in the car, my service engine light was on. I had my state emissions test and in turned failed because the service engine light is on. I took the car to the dealership and it was determined that the rear speed sensor malfunctions which has in turn caused my abs light and the abs light caused my service engine. The dealer says that there is nothing wrong with the brakes or abs and no reason to have failed emissions. I'm working to replace the speed sensor.