Symptoms
- Transmission-specific icon lit on the dash
- Possibly paired with reduced performance or limp mode
- May come with unusual shifting behavior
- Light may be steady or flashing
Likely causes
- CommonLow transmission fluidFluid level sensors or pressure sensors can trigger the light when fluid is low.
- CommonOverheatingA temperature sensor can trip the light when the transmission runs hotter than normal.
- CommonFaulty sensor (speed, position, or temperature)A failed sensor sending bad data is one of the most common triggers.
- PossibleSolenoid or valve body faultElectrical or hydraulic faults in the shifting mechanism can set this light.
- PossibleInternal mechanical wearMore significant wear can also trip the warning as a protective measure.
What to do
- Check the transmission fluid level and top off if low.
- Get the trouble codes read with an OBD-II scanner, which will point to the general system involved.
- Note if the car is also shifting oddly, stuck in one gear, or losing power.
- Avoid highway speeds or towing until the codes are checked, in case the transmission is in a protective mode.
- If the light is flashing rather than steady, treat it as more urgent and avoid driving if possible.
- Have the specific fault diagnosed at a shop rather than just clearing the code, since it will likely return.
- Address the underlying cause (fluid, sensor, or mechanical) rather than driving indefinitely with the light on.
Tools and parts
- OBD-II scanner
Transmission fluid (correct type for vehicle)Search: “transmission fluid type for [make model year]”
When to call a pro
See a mechanic to read the codes properly; a transmission warning light should not be ignored since the computer often limits function to prevent further damage.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.