ABS & TCS lights on '99 Bonneville

Both ABS and TCS (Traction Control System) lights have come on and off over the past year. This summer, they came on when the weather was really hot
(over 90) and I began thinking maybe the bearings were affecting the sensors.
Now that it's cool (under 60) they are coming on frequently right after starting. Sometimes I can move 20 feet and restart the car and they both go out.
A week ago (both lights were off) I made a hard stop on wet pavement, and I think the ABS kicked in for an instant, and both these lights popped on simultaneously. Since then they've been on more than they've been off.
I figure I'll have to probably take the car in to a GM dealer.. but is there anything I can do on my own to troubleshoot it before resorting to a dealer?
Thanks Dave
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If you are going to take it to the dealer, anything you do in your driveway would be a waste of time. Unless of course you have a scan tool and can pull the ABS/TCS codes.
Sounds most likely as if there is a bad sensor/wiring at sensor. This is pretty common. The best you can do without a scantool is check the connections at each sensor and measure the resistance of each sensor. If one is higher than the rest or one is open, that's your problem.
All that being said, have the codes read and following the diagnostic chart for that code is the best route. Randomly diagnosing things is essentially a waste of time.
Steve

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