What causes trac off light to stay lit?

have the dtc's checked in the abs module.

Since you had tires installed, check the electrical connections on the wheel speed sensors at the hubs.

My sunfire was acting weird and tried unplugging the MaF sensor to see if I could get it to run a little leaner, the traction light pops on and the car shifts like its being rear ended, after a short jaunt the engine light comes on, cause I know it threw a code for having the MaF sensor unplugged. Plugged the sensor back in, car shifted fine and Trac light went out. The trac light is more than for the Traction control, its kinda of a warning light letting ya know there is a problem with a sensor somewhere, like a pre-warning, when it throws the engine light on is when ya know ya have a code fired up and something the computer picked up that it doesn't like. If ya changed tires, especially a different size, it will turn on the trac light until the computer figures it out, if the trac light stays on and the engine light shows up, then pretty good sign they knocked a sensor lose somewhere on the hubs.