Short answer
The transmission temperature light means the automatic transmission fluid is overheating. Pull over when it is safe and let it cool, with the engine idling in Park unless your manual says otherwise. Overheated fluid breaks down quickly and can damage the transmission, so find out why before towing or climbing again.
- Also shown as:
- Transmission overheat light · AT temp light · “Transmission hot” message
- What it looks like:
- A gear with a thermometer inside it, usually red or amber.
Is it safe to keep driving?
No. Pull over and let it cool with the engine idling in Park. Overheated fluid breaks down and destroys the transmission.
Stop driving now if:
- The light comes on while you are driving — pull over now rather than at the next exit.
- The transmission slips, flares or shifts harshly, or you smell burning fluid.
- The light comes back on soon after cooling down, even without a heavy load.
What causes the transmission temperature light?
Most common first. Symbols and meanings vary by manufacturer; your owner's manual has the definitive meaning for your model.
- Towing or heavy load in hot weather. Towing, steep climbs and stop-and-go traffic in the heat put the most strain on the transmission and heat the fluid fastest.
- Low or degraded transmission fluid. Too little fluid, or old fluid that has broken down, cannot carry heat away. Dark fluid with a burnt smell is a warning sign.
- Blocked transmission cooler. The fluid is cooled through a radiator section or separate cooler; a blocked cooler or line traps the heat.
- Internal transmission fault. A slipping clutch or torque converter generates heat inside the transmission itself; overheating without a load points here.
What should you do right now?
- Stop and let the transmission cool before continuing.
- Check fluid level and condition if your car has a dipstick; dark or burnt-smelling fluid needs changing.
- If you are towing, lighten the load or take a slower route with fewer climbs once it has cooled.
- If it recurs without a heavy load, have the transmission inspected.
What does the fix usually involve?
A shop checks the fluid level and condition, the cooler and its lines, and reads the transmission codes for slipping or solenoid faults.
Common repairs: a fluid service with the fluid the manufacturer specifies, a cooler or line repair, and for regular towing an extra transmission cooler. Internal damage means a rebuild or replacement.
How much does it cost to fix?
$150 – $4,000
A fluid service at the low end; a transmission rebuild at the high end.
A typical range, not a quote. Actual cost depends on the car, the shop and the fault.
Common questions
Why should I idle in Park instead of switching off?
On many automatics the pump only circulates fluid through the cooler while the engine runs, so idling cools it faster than switching off. Your owner's manual has the instruction for your car; follow that if it differs.
Does towing void my transmission warranty?
Generally not, if you stay within the towing limits in the owner's manual and follow the maintenance schedule it gives for towing. Warranty terms are the manufacturer's, though, and damage from towing beyond those limits may not be covered — read your warranty booklet.
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