I have a 2005 malibu,

t/c is a traction control . it could be a fauly wheel bearing sensor or a faulty ebcm module.
is your anti lock brakes light on too? if so then its probally a wheel bearing or wheel bearing wiring there are a few things you can do to find out if your wheel bearing sensors are working. if you have a multi meter attach it to the terminals on the wheel bearing itself it should give a reading of 1080 - 1180 ohms normally for front and a little less for the rear.

The "t/c" stands for traction control. The light is indicating the traction control system will not function if need as in the event of a skid.
There are a couple of reasons why the light may have come on:

• If you turn the system off by pressing the
TC (traction control) button located on the center
console, the light will come on and stay on. To turn
the system back on, press the button again and
the warning light should go out.
• If there’s a brake system problem that is specifically
related to traction control, the ETS will turn off and
the warning light will come on.
If the traction control system warning light comes on
and stays on for an extended period of time when the
system is turned on, your vehicle needs service.

Hope this helps, let me know.
Regards,

2002 Trailblazer ABS light and Brake light on and the blower on A/C doesn't work

A lot of people forget to mention one other thing. I'm not sure if all of GM's vehicles with Anti-lock brakes do the same thing but I know the Firebird and Camaro do. If both bulbs in the third brake light go out, both the "Brake" light and "T/C" light come on. I took my car in for repairs and GM wanted an un-godly amount to fix the problem so I didn't fix. I decided to tackle the problem myself. It didn't make any sense to me when I would start the car and hold the brake pedal at the same time, the lights wouldn't come on until I released the brake pedal. So I knew it was something simple. I had a stereo system in my car and never thought to check the third brake light bulbs. I noticed they were out while backing my car into it's resting place and saw the bulbs out. I immediately replaced the bulbs, cranked the car and what do you know....the lights never come on. The dealership was trying to rape me on this repair and what's bad is they probably knew that it was just 2 little bulbs you could buy for $1.00.