96 PA ABS - grabs when stopped - no codes

My 96 PA ultra ABS occasionally grabs the left front wheel when I try to go forward from a stop. The dash shows ABS and Traction fault lights but no codes show up with the tester. My mechanic inspected the brakes and they look fine; he also noted that the fault lights go out as soon as the tester is connected. The dash faults are present about 75 percent of the time. There is no pull or drift when driving but when leaving a stop it feels like its locking up. Looking for suggestions before I disable the system.

I had the same trouble on my 96 PA.I took it to a shop and had the codes scanned on the abs and it showed a right front short to ground.I replaced the hub and sensor assy and everything is fine now.You may want to try another shop to scan your abs system.I paid $35 to have mine scanned and then replaced the hub myself.