why is the trac light on?

Is it just the trac light? Or is it the ABS brake light as well? It's either going to be a bad wheel bearing, because the Trac control works with the ABS and both sensors are built into the bearing, or the wire that plugs into the wheel bearing is broke, rubbed through or shorted out. Very common problem with the GM vans and W platform vehicles (Grand prix, Impala, Monte Carlo ect)

Ok. Service Engine Soon light was/is on. Code came up po449. Replaced evap. emission vent valve solenoid. Also removed air filter and blew out lots of dirt/ sprayed throttle body out real good. Disconnected battery for 10 minutes, reconnected, turned ignition key to on position, pumped accelerator pedal slowly 3 times within 5 secs. turned key off 5 secs., then started 2004 Pontiac Montana up and not only is service eng. soon light on, but service traction and trac off lights are both on and car runs terrible, but ran perfect before any of my obviously inferior handywork and I've been working on cars for over 45 years!