Wheel Hub or ECU?

My SVS, ABS and TRAC OFF lights are all on. Last time this happened it was a broken wire to a wheel hub, repaired with a splice. This time, my mechanic tested the voltage at each hub by spinning the wheels, all are OK. Wires look good. Maybe the ECU? But it's a very expensive part to replace. Is there a definitive test to determine if it's a hub or the ECU? Any advice is welcome.

Well the best "test" would be to plug it into a Tech 2 or equivalent diagnostic machine and see what the codes are.

A standard code reader wont do it, it has to be something capable of reading ABS codes.

I believe Equus had a ABS reader that I saw at Sears. ~$80

Go the Tech2 route and find out what is wrong. -instead of just throwing money at it.

there is a $99 abs upgrade from Equus and their newer $200-300 scanners have the abs built in.

If it were me trying to save a few bucks i would check each wheel sensor (wires and plug ins)...make sure there's no damage or bad connections, next step is to get it scanned.
you could go ahead and replace the wheel hubs like I did, but that's only because the bearings were all worn out anyway. If your bearings are fine then defiantly get a proper ABS scan

Thanks, everone. Tech 2 is the way to go.

Whats the tech 2 who sells it, Autozone sells something for 200 called abs scan GM FORD CHRYSLER Only, if it could do all cars I'd just buy it, but ObD2 up cars

Tech2 is GM's scanner for pulling codes for ABS, transmission and pretty much any code that trips the "Service Vehicle Soon" light rather than the "Service Engine Soon" light. It costs quite a bit of money; it's not something that the average "do it yourselfer" would have.

I haven't had a chance to get the Tech 2 scan, however, now that the temperature has been below 30 here, the lights went out and I have ABS and variable steering back! I haven't driven the car long enough to fully warm upthe engine (just to the train station and back) so I don't know if the problem will return when warmed up. Any thoughts on narrowing down the cause of the problem given the reaction to the cold temp? Thanks.

likely there is less moisture below freezing, Mine occasionally acts up and trips the ABS/SVS lights in heavy rain...no doubt the fault of a bad wire or connection on one of the wheel speed sensors. I would un-plug and re-seat all the plastic connections, making sure they are clean and dry, and also making sure they fully click in to place to make a good connection. Look over any exposed wires for breaks or signs of a possible short.