* Faulty Coolant Temperature Sensor: This is the most likely culprit. The sensor itself might be malfunctioning and sending inaccurate readings to the computer. A relatively inexpensive and easy fix.
* Low Coolant Level: Even if you recently checked, double-check your coolant level. A low level can cause overheating. Look for leaks around the radiator, hoses, and water pump.
* Coolant Leak: A small leak might not be immediately obvious, but even a slow leak can eventually lead to overheating. Inspect all hoses, clamps, the radiator, and the water pump for any signs of leaks.
* Faulty Thermostat: The thermostat controls coolant flow. If it's stuck closed, the coolant can't circulate properly, causing overheating.
* Water Pump Failure: If the water pump isn't functioning correctly, it won't circulate coolant effectively, leading to overheating.
* Radiator Problems: A clogged radiator (internal blockage or external debris) restricts coolant flow.
* Faulty Radiator Fan: The radiator fan helps cool the coolant. If it's not working, the engine can overheat, especially at idle or low speeds. Listen for it when the engine is running.
* Blocked Airflow to Radiator: Something might be blocking the airflow to the radiator, preventing it from cooling the coolant efficiently.
What to do immediately:
1. Pull over safely: Do not continue driving with the overheating message displayed. Continuing to drive could cause serious engine damage.
2. Turn off the AC: As the message suggests, turning off the AC reduces the load on the engine and may help slightly.
3. Let the engine cool completely: Do not attempt to open the radiator cap until the engine is completely cool. Hot coolant under pressure can cause severe burns.
4. Check the coolant level: Once cool, carefully check the coolant level in the overflow reservoir (not the radiator itself). If low, you might need to add coolant (use the correct type – consult your owner's manual).
5. Have it professionally diagnosed: Take your Impala to a mechanic or trusted auto repair shop for a proper diagnosis. They can identify the root cause and perform the necessary repairs.
Ignoring the overheating warning can lead to a cracked engine block or head gasket, which are very expensive repairs. Get it checked out as soon as possible.
