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SensorsSeverity Medium: diagnose soon

P0116Engine Coolant Temperature Sensor 1 Circuit Range/Performance

What it means

The engine coolant temperature sensor reading is plausible electrically, but doesn't match the other temperatures or doesn't change as expected while the engine warms up. The ECU uses coolant temperature for cold-start fuelling, idle speed, the radiator fan and the temperature gauge.

Symptoms

  • Hard starting, rich running or black smoke
  • Radiator fan running all the time
  • High idle or wrong temperature gauge

Common causes

  • Thermostat stuck open (engine doesn't warm up as expected)
  • Sensor drifting
  • Low coolant level leaving the sensor in air

What to check first

  1. Graph coolant temperature from a cold start: it should rise steadily to 85–105 °C
  2. Compare the reading with an IR thermometer at the sensor housing
  3. Check the coolant level and bleed the system
Can I drive with P0116? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0116

Coolant temperature sensor (ECT)Wiring, typical values, multimeter and scope tests

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P0116: questions and answers

What does P0116 mean?

P0116: Engine Coolant Temperature Sensor 1 Circuit Range/Performance. The engine coolant temperature sensor reading is plausible electrically, but doesn't match the other temperatures or doesn't change as expected while the engine warms up. The ECU uses coolant temperature for cold-start fuelling, idle speed, the radiator fan and the temperature gauge.

What are the symptoms of P0116?

Hard starting, rich running or black smoke. Radiator fan running all the time. High idle or wrong temperature gauge.

What causes P0116?

Thermostat stuck open (engine doesn't warm up as expected). Sensor drifting. Low coolant level leaving the sensor in air.

How do you diagnose P0116?

1. Graph coolant temperature from a cold start: it should rise steadily to 85–105 °C 2. Compare the reading with an IR thermometer at the sensor housing 3. Check the coolant level and bleed the system

Can I drive with P0116?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.