I have a 2004 Grand Prix. the ABS/traction control/Variable effort steering warning lights come on. Any suggestions

Have the vehicle scanned for trouble codes along with ABS codes. This will let you know whats going on.

Good advice. Always scan for codes first. Also check front wheel bearings. Worn bearings will often cause ABS/traction control issues. I'm not sure that that will show up on a scan. The scan will likely just indicate the problem is with a wheel sensor. Of course a new wheel bearing will include a new sensor. And replace the bearing with a good american made one if you're planning to keep the car. The cheap import ones often only last about a year.

I've just had the similar problem recently and I took it to my mechanic and he ran a diagnosis test and found that it was my ABS module box there was no power coming from the C1 wire line all other lines we're ok except for that one they checked to see if it was the wire but it wasn't it was actually the module box and I had to replace it, once it was done boom !!! No more service variable effort steering service warning everything is good.