Transmission temperature warning light

Red thermometer inside a gear, on many automatics The transmission fluid is too hot. It mostly appears under hard work, such as towing a trailer. Stop when it is safe, put the transmission in Park or Neutral and let the engine idle, or run slightly faster than idle, until the light goes out. Then you can carry on, ideally with a lighter right foot. Do not keep driving with it lit. Overheated fluid can eventually wreck the transmission, and in the worst case it can boil over onto hot engine or exhaust parts and start a fire. If it keeps returning, book a check before the next tow.