My '08 Cobalt ABS, Traction Control and Stability Control light comes on either immediately after I start up or within about 40 minutes after start up. I know the wheel speed sensors may be bad but is there an easy way to check them? Someone mentioned the transmission speed sensor but if it was bad, my speedometer wouldn't work, right? Dealer wants at least $65 just to scan the car and I don't want to put any more money into it as I'm trading it in. Comments or advice appreciated.