We just bought an immaculate 1995 Lexus LS 400 with 145,000 miles. My wife was driving it today and the "TRAC" light came on. My repair shop said bring it right in and do not drive it. But a Toyota dealer said it is not a big deal, probably a computer glitch, so go ahead and drive it and bring it in next week.
What is TRAC and is it serious? This is a really beautiful car and I want to enjoy it for years.
The dealership response was semi-correct. The TRAC indicator lighting up on the instrument panel signifies a fault in the traction control system. But the only immediate impairment is traction control being disabled until the problem has been corrected. This is to ensure safe operation of the system. I wouldn't consider that an emergency, but it certainly should be repaired.
Traction control uses two processes to increase traction at the drive wheels (rear on the LS). One of those is the throttle. When wheel speed sensors indicate that the rear wheels are spinning faster than the front, the system closes the throttle an appropriate amount to lower engine speed and reduce wheel slip. Traction control is also an integral part of the antilock braking system. Again, when wheel speed is detected to be faster at the drive wheels, the brakes are applied automatically in a pulsating fashion to reduce wheel slip under poor traction conditions -- kind of the opposite of how ABS lets off of the brakes in a pulsating fashion to reduce skidding and aid in stopping.
You may have previously noticed the "SLIP" indicator on the instrument panel lighting up for a few seconds while accelerating from a stop on a slippery surface. That's the traction control system telling you that it's engaged and attempting to reduce wheel slip to get you on your way.
Chances are there is a trouble code stored in the ABS/TRAC electronic control unit memory which will lead a technician to the cause of the failure.