Anti lock brake light

I have Dodge 2004 , 3500 . The anti lock and brake dash warning lights came on and also a couple of ding sounds. I checked the fluid, it was OK, plug ins etc. What could be wrong? wheel sensors ? Will a code scanner tell me anything? How to trouble shoot? No apparent problem while putting on the brakes.

Check the wheel sensors to make sure they are clean.

I'll check the wheel plug ins. Is there a way to check voltage ? but then what should it read?

Sensor on top of the rear end housing.