Abs light still on after 3 dealership "fixes"

Start looking at the wheel speed sensors and go back from there. I think you’ll eventually find something with a fuzzy blue sweater on it. A plug or a length of wire with the insulation compromised. Anomalies when the spray flies tends to point that direction.

 

I have found several problems on a truck at times. Chaffed ABS sensor wires, intermittent failing ABS ECU and ABS sensor wire with too much tension on it and it had pulled away from tone ring on the steer axle left side. Driving the truck around the shop with Wabco Toolbox abs software up running and watching the wheel speed found the speed not changing on left steer and that one sensor was causing the traction control light to come on and stopped it from accelerating. Interestingly, there was no fault for left steer losing signal. You may find the Meritor-Wabco ABS Maintenance Manual MM-1719 helpful. Just google "Maintenance Manual MM-1719" In that manual it shows fault 791-7 "Wheel speed sensor (Drive axle left) - mechanical system not responding or out of adjustment. There is much more on that fault in manual. Also, on trucks with DISC brakes we have seen tone rings damaged. I guessing that your truck probably has Wabco/ Meritor ABS but if you post the last six digits of your VIN we can get you more accurate information.