Low coolant temperature indicator (blue)
A blue thermometer light that shows the engine coolant is still cold.
How to read it
The symbol is the engine coolant thermometer standing in liquid, the same shape as the high temperature warning light, but lit blue. Honda calls it the low temperature indicator and says it comes on when the engine is cold; Mazda says it stays on while the coolant temperature is low and goes out once the engine is warm.
Also searched as: blue coolant light, blue thermometer light, cold engine light.
Dashboard symbols vary by manufacturer. The vehicle's owner's manual or a qualified mechanic can say what a light means for a particular vehicle.
What the manual says to do
Honda’s guide says that if the indicator is still on when the engine is at normal operating temperature, the owner should see a dealer as soon as possible. Mazda’s manual says a light that stays on after the engine has warmed up could mean the temperature sensor has a malfunction.
Blue or red
The blue light is information: the engine hasn’t warmed up yet. The red light with the same shape is the high temperature warning.
More dashboard warning lights
Sources
- 2009 Honda Fit Dashboard Details, American Honda Motor Co., Instrument Panel Indicators
- Mazda3 Owner’s Manual: Low Engine Coolant Temperature Indicator Light (Blue), Mazda Motor Corporation, Warning/Indicator Lights
Last reviewed September 28, 2026 by Rory Hansen. How we research