Transmission temperature light
A gear or cog with a thermometer, amber or red
Do not keep driving it · Red means stop
Transmission temperature light
Stop driving as soon as you can do so safely, and let the car sit and cool down. This one is red, and it means the transmission fluid is running hotter than it should. Heat is what kills automatic transmissions. Continuing to drive on this light is how a repair job turns into a replacement job.
The light means the car has a sensor reading the temperature of the transmission fluid, and that reading has crossed into a range the manufacturer considers dangerous. Transmission fluid does two jobs: it lubricates the internal parts and it carries hydraulic pressure that makes gear changes happen. When it gets too hot, it breaks down, stops protecting those parts, and clutch plates and seals start to fail. That damage does not reverse itself once it happens.
Once the light is on, pull over when it's safe, put the car in park or neutral, and let it idle or sit with the hood up for a while to bring the temperature down. If the light goes off and stays off, you can generally continue at low speed to get the car looked at. If it comes back on, stop again. Towing is the safer choice if you have any doubt.
The common causes, most likely first:
Low transmission fluid, often from a slow leak, is the most frequent cause. Low fluid means less material to carry heat away and less hydraulic pressure, so things run hotter and work harder. Towing heavy loads or driving in stop-and-go traffic in hot weather can push a transmission that's otherwise fine into overheating, especially if the fluid is old. A failing transmission cooler, or a cooling line that's blocked or leaking, will also cause this. Less commonly, the transmission itself is starting to fail internally, and the heat is a symptom of that rather than the cause.
Putting it right starts with checking the fluid level and condition. If it's low, we find the leak and fix it, then refill with the correct fluid. If the fluid is old or burnt-smelling, it usually needs to be changed rather than just topped up. If the cooler or lines are the problem, those get repaired or replaced. If the transmission has already sustained heat damage internally, that's a bigger job, and we won't know the extent of it until we've had a look. We can tell you which of these it is once we've checked the fluid and run a diagnostic, but we won't guess at a cost before that.