ABS Problem

I took my 2000 F-150 to mechanic b/c my ABS light came on. I typically do all my repairs but did not have any ABS scanning tools to trouble shoot this problem. After the mechanic performed his diagnostics, he said my ABS computer/module needed replaced. He said it would be around $400 dollars. Reluctantly, I paid for the repair and my ABS light went off. I figured that the problem was solved.

A few months later I decide to test out the ABS (out of fun) in the snow. While playing around, I noticed my ABS pump did not work. I decided to try in a long skid and nothing happened. It felt the same as not having any ABS brakes like on my old Ford truck. All wheels locked up. There is no ABS light on to signal any problem.

Could the repair have been done incorrectly or could there be another problem?

Note: Before and after the repair, the front left caliper has notoriously gone bad. I have replaced it 3 times and went through 3 rotors. I have bled the system correctly and there seems to be no structural or mechanical defects. There are no leaks coming from the master cylinder or ABS module. The vehicle has never been in a collision and is in excellent physical and mechanical condition. Any advise?

Thanks

Tye

2000 F-150 Super cab 4WD
4 Wheel ABS
98,000 miles