Cooling system
P0116 — Engine Coolant Temperature Circuit Range/Performance
The coolant temperature sensor reading does not change or follow the expected pattern as the engine warms up. The ECU relies on this signal for fuel, idle and fan control.
Common causes
- Faulty coolant temperature (ECT) sensor
- Low coolant level or air in the cooling system
- Thermostat stuck open or closed
- Corroded connector or wiring
- Faulty cooling fan control
Symptoms
- Hard starting or rough idle
- Cooling fan runs wrongly
- Temperature gauge behaves oddly
- Check engine light
How to check
- Check the coolant level and top up/bleed the system if needed
- Compare ECT reading with a real thermometer on a cold engine
- Watch the live value as the engine warms up and look for jumps or a flat line
- Test the thermostat and sensor
Can you keep driving?
Drive carefully and watch the temperature gauge. If the engine really overheats, stop at once.
Related codes
Frequently asked questions
- What does P0116 mean?
- The coolant temperature reading does not make sense compared with how the engine heats up.
- Can a thermostat cause P0116?
- Yes. A thermostat that is stuck open or closed changes warm-up behaviour and may trigger it.
General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.