Volvo VNL660 Traction Control Problem - Kills Engine - Won't Turn Off

Ok, so my brother runs a 2001 Volvo VNL660. I used to run it myself, and the traction control worked great once upon a time. Turning it on in a slippery parking lot gave me at least triple the traction. But the last year or so the traction control ends up making things worse. It works by actuating the brakes on slipping wheels. But lately it has been not just slowing the slipping wheel, but locking it up. And it also seems to be slow to release. So what happens is as soon as a wheel is locked by the TCS, it causes the system to think the other wheel is now slipping, so it locks that wheel, but it is slow to release the first wheel, so now two wheels are locked. Basicly if you are on a slippery surface the TCS locks so many wheels at once that the engine will kill if you don't clutch quick enough.

There are no codes being stored in the computer for the traction control system, or for anything else. Also, most of the time turning the TCS switch off has no effect. Sometimes it does, but usually not.

So basicly this thing gets stuck all the time. As soon as you hit some mud or snow the TCS locks the wheels and kills the engine. A tow is needed to dry pavement to get on the road again. Driving on dry pavement results in no unusual symptoms. Any ideas besides "take it to the dealer"??? We have a fully equipped shop, just no ideas...

 

Those are good ideas. I'll look into them. The brakes work fine, good pads, no camover, no abs faults stored.