Brake problem?

Redfish is right.
I had problems with the proportioning valve which is located in the frame C channel in FRONT of the drivers foot area. There is a secondary valve built into it whose name escapes me right now. This valve was messed up on my truck, turning on the ANTILOCK warning light, but like Redfish said, the brakes will operate normally even with the light on. I was able to clean and repair this small valve. It lasted a while, then the light came on again.
Having said all that, there is also an exciter mounted on the differential which reads wheel speed. There could be build up metal shavings on it causing it not to send a signal. My truck has a Dana 60 rear, and it is mounted up top of the carrier.
If you look in the service manual, there is a rather long testing procedure you can follow to diagnose the RWAL system. I started to test mine, and after the electrical part of the test passed, I kinda gave up as I didn't want to spend money for something I really didn't like anyway. I would rather drive with conventional brakes. I know I can stop a vehicle better than some computor can, but that is my own opinion.

If there is no pedal, you either have air in the system somewhere, or a bad master cylinder.
Keep looking dude, and good luck!!!

George