Bob R. 4/19/2010DSC works with the ABS system and Engine Computer. There are sensors on each wheel, sometimes with a green wire going to them. (There are also separate wires for the brake wear sensors). Check the contacts where the wires plug into the harness inside each wheel well - unplug and replug. If that doesn't help, remove the sensors where they bolt onto the wheel hubs. Usually one 10mm bolt, and remove them and clean any rust off of them and the hole they mount into. This is quite often a bad ground if the light is intermittent, especially if you are in areas where they use salt on the roads. If that doesn't do it, then it could get costly for a diagnosis. Unless it's the fan not working, your A/C probably just needs a shot of Refrigerant R-134a. Buy a kit with a gauge on it at Walmart for $15.00 and follow the directions exactly - don't overcharge it..