I have replaced most of my brake line. Now I am getting intermittent brake/abs light. It dosen't come on while I am driving it comes on sometimes when I start the truck, mabie once every 10 starts, and will not clear until I shut off and restart the truck. Is this the speed sensor on the rear diff, it seems that when it goes bad that it will give the errors all of the time? If I were to buy a code reader would it tell me?

 

Auto Zone will do a check your check engine light for free and I am pretty sure it is the speed sensor like you said.