91 Ford Bronco Anti Lock/Brake Light Indicator

My friend's 91 Ford Bronco had the rear brakes replaced two months ago and front six months ago. System has been bled and checked with no apparent fault but the Anti Lock and Brake Light Indicator comes on within the first two miles of driving every time. The brakes are not hot or significantly different in temperature and once the vehicle is restarted the same scenario plays out.
No flashing code both lights just come on steady.
I'm guessing it is either the Hydraulic Control Unit (HCU) along the frame or the brake control unit under the dash. Is there a way to check or eliminate either? What type of abs system do you have? Does it have a 'normal' master cylinder, or a setup (in it's place) with a pressure accumulator and pump that runs periodically to keep the accumulator pumped up?

In either case, the trouble is likely a wheel speed sensor. You say no flashing code... Have you scanned it to verify there's no codes stored in the abs computer? (They sell GM trouble code scanners that also scan the abs computer)

Make sure all 4 wheel speed sensors have intact and plugged-in wires. Also, the tone ring (what the speed sensor 'looks' at to determine wheel speed) must not have teeth missing, or gunk caked between the teeth.

Other than that, you'll need to have the system scanned (or do it yourself). If that light is on, then there’s a 99.9% chance there is a trouble code stored in the computer system that handles the abs. I think this truck has the anti lock sensor in the rear differential.....right? if so try replacing this cheap part first. Sometimes you can take this sensor out of the rear end housing and clean off the metal shavings that get stuck to it and reinstall it. if this doesn't help the electro hydraulic valve would be the next step.Car Repair Talk's forum.