my recent purchased 1998 328i ....traction control not responding...no light no change in driving response....

what do I check for....fuse ,switch,sensor or go 2 dealer and get boofed...?

Is the light off before you hit the switch? If it is on after starting the car and before hitting the switch there's a fault somewhere in the system. In a like manner, if there's a fault and the bulb is burned out from being on continuously hitting the switch will have no affect. In eiter of those cases having the fault codes read out will probably be illuminating.

It may be working and the light may be burnt out.

Put the car on blocks and give it a little gas...you should hear all kinds of thumping. Hit the button and do the same again....you should just hear the tires spinning.

I would need some advice troubleshooting the following situation with my 2000, 528it: Traction Control light is on from the moment the engine is started, ABS is working fine. Can not turn light off using the TC switch. I would appreciate some ideeas what to look into.

on an e39 your probably looking at a wheel speed sensor or a DSC control module. Don't be surprised if its both.