Most newer vehicles are equipped with a coolant level sensor. This sensor measures the amount of coolant in the vehicle and alerts the driver, via a light, if the level drops below a certain amount. This system is imperfect because the light can be triggered for several reasons.
A low level of coolant is the main reason this light come on. If the coolant level is low, add the recommended amount of coolant to the engine to turn the light off. Keep in mind that the cooling system is sealed and your vehicle should not lose coolant, so a proper diagnosis can identify why your vehicle is losing coolant.
The coolant level sensor is sensitive to contamination. If it gets covered in sludge from the cooling system, it cannot properly read the coolant level and can trigger a false reading. This is common in newer General Motors vehicles that use Dex-Cool antifreeze.
As with most auto parts, a cooling sensor and its related components can go bad. The most common cause is a failed sensor; a replacement sensor will fix the problem. On occasion, the wiring to the sensor or even the vehicle's computer can fail, triggering the warning light.
