Why is the trac light on

Get the trouble codes read. See this post on what ABS light means

https://ricksfreeautorepairadvice.com/abs-light-on/

This means there is a problem with the trac and abs system. the way it works is that when the computer sees a problem with the abs or trac system it turns them both off. also if the check engine light is turnned on due to a problem the computer shuts down the trac and abs system as well due to the computer not being able to control the trac or abs system when there is a engine problem.

The first step here would be to have the computer scanned and get any stored codes out to find out where the problem is. Have the computer scanned for codes first.

Hello anber...the "Trac OFF" light comes on when there is a malfunction in the ABS because the traction control system uses the ABS sensors and other components to apply brakes to the slipping wheel so that the other wheel will get some power. Not as good as a limited-slip diff, but better than nothing. With the ABS reporting a fault, the Traction Control cannot function, and its computer disables it--hence the light. Fixing the ABS should fix the Trac problem. I would start by checking the sensors and making sure the master cylinder is full of brake fluid. I hope this helps.

the trac light is the traction control, the abs light means the antilock brake system is not functioning properly. the trac control is no issue. the abs will not cause the brakes to fail but they will lock instead of pulsing.

ANY TIME ABS LIGHT OR TRAC LIGHT COMING ON THAT MEANS EITHER ONE IS NOT WORKING NOT GETTING NO OR ENOUGH POWER.CHECK ABS FUSE AND RELAYS. IF RELAY AND FUSE OKAY.MAKE SURE YOUR ALTERNATOR VOLTAGE OUT PUT AT BATTERY SHOULD BE 13.5 TO 14.5 VOLTS IF 11.0 VOLTS DUE TO VOLTAGE REGULATOR FAILURE. THAT WILL CAUSE ABS AND TRAC LIGHT TO COME ON.IF ALTERNATOR CHECKS OUT OKAY.TAKE VECHICLE TO GARAGE OR DEALERSHIP THEY HAVE TO SCAN THE ABS BRAKE SYSTEM.

means the traction control module is bad. That light is suppose to come on when you lose traction to let you know the traction control is kicking in.

If your ABS light is on as well, have a shop scan it (it requires a special scanner). If it's just your Trac light without ABS, it is most likely a sensor under the hood at fault. If you are getting a check engine light as well, get the codes read!
This happened to me without an ABS light and it was the upstream O2 sensor. The reason it throws the Trac light is because if any components that the traction control uses (ignition, fuel) are affected by a bad sensor, the PCM shuts down traction.
In fact, when I replaced the O2 sensor, a handful of other little issues resolved as well.
If you do have an ABS light on, it could very well be a wheel speed sensor.

This generally means that you have a problem with your brake system. I would try opening the hood and checking the brake fluid level on your Avalon.

If your ABS light is on as well, have a shop scan it (it requires a special scanner). If it's just your Trac light without ABS, it is most likely a sensor under the hood at fault. If you are getting a check engine light as well, get the codes read!
This happened to me without an ABS light and it was the upstream O2 sensor. The reason it throws the Trac light is because if any components that the traction control uses (ignition, fuel) are affected by a bad sensor, the PCM shuts down traction.
In fact, when I replaced the O2 sensor, a handful of other little issues resolved as well.
If you do have an ABS light on, it could very well be a wheel speed sensor.

ABS light is on & Trac off light is on. Transmission does not seem to be shifting with any problem. What should I look for?