P0116: Engine Coolant Temperature Sensor 1 Circuit Range/Performance

Common causes

• A coolant temperature sensor that reads inaccurately
• A thermostat stuck open, so the engine warms up too slowly
• Low coolant or an air pocket around the sensor
• A loose or corroded connector causing an intermittent signal

Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.

Symptoms

• Check engine light
• A temperature gauge that is slow to rise, erratic or reads low
• Weak cabin heat if the thermostat is stuck open
• Poorer fuel economy or hard starting

Is it safe to drive?

First make sure the engine isn't really overheating: if the gauge reads hot, you see steam or a warning light, stop and let it cool, and don't drive it until you know why. If the temperature is truly normal, it's usually OK to drive gently to a shop, but fix it soon.

How to check it with a scanner

1. Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
2. Check the coolant level only with the engine cold; never open the radiator cap or pressurized reservoir on a hot engine.
3. After the car has sat overnight, turn the key on and compare coolant temperature with intake air temperature in live data; they should be close.
4. Watch the coolant reading as the engine warms up. A slow climb that never reaches normal operating temperature points to the thermostat; sudden jumps point to the sensor or connector. Keep hands clear of the belts and fan, which can start on its own.
5. Replace the sensor or thermostat only with the engine cold, then refill and bleed the cooling system following your vehicle's procedure.
6. After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.

A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.

Questions

Related codes

• P0128: Engine not warming up fully (thermostat)
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