95 K3500 ABS problem

I have a 7.4L 4X4 K3500. My ABS doesn't work at all. If I lock up the brakes my wheels lock up. I have checked my fuses and all is okay. Can anyone point me in the right direction?

TIA

Is your ABS light on? If it is try accessing the codes by jumping the A & H terminals on the ALDL connector. ABS systems dont always keep the brakes from locking up on dry pavement they go into action when they sense a wheel spin. Try it on a wet surface carefully.

I have no lights on the dash indicating a problem. I tried several things this winter when the roads were snow covered. Everytime the wheels would lock. The ABS motor never operated.

Have you installed anything in your brake system lately? Some times air can get trapped in the abs pump.

The rear brake lines were changed out about 1 year ago. The brakes seem to work good and don't act like there is air in the system. How can I tell and is there any way for me to bleed the ABS system if there is?