Flashing brake light

I have a 1989 chevy S10 Blazer that has 190,000 miles on it. My problem is that the brake warning light keeps flashing and even though I have replaced the wheel cylinders, hoses, bled the brake lines and replaced the speed sensor the flashing wont go away. I have reset the computer to empty the codes, the code I keep getting is 10, I noticed that once I reset the computer the flashing goes away until the truck reaches 40MPH then it will come back on. I am stumped and dont know what to do to resolve this I am thinking of replacing the RWAL ECU but I dont know if this will resolve the issue I appreciate any help in this matter.