AutoDiag

P0116

Engine Coolant Temperature Sensor 1 Circuit Range/Performance

Moderate· Fix soonDIY friendlyPowertrainGeneric, all makes

What it means

The engine coolant temperature (ECT) sensor is sending a signal that is electrically valid but does not make sense compared with other sensors. The engine coolant temperature (ECT) sensor tells the ECU how hot the engine is, which affects fuel mixture, idle speed, cooling fans and the temperature gauge. This usually points to a sensor that is reading wrong, or to a real mechanical problem it is reporting correctly, rather than a broken wire.

Is it safe to drive?

Drivable with care, but you may not get a correct temperature warning. Check the coolant level first and watch for real overheating.

Symptoms

  • Check engine light on
  • Temperature gauge reading wrong or not moving
  • Cooling fans running all the time
  • Hard starting, especially cold
  • Poor fuel economy and black smoke

Probable causes

Most likely first

  1. 1Low coolant level leaving the sensor in air
  2. 2Thermostat stuck open
  3. 3Sensor reading drifting compared with an infrared thermometer
  4. 4Failing sensor giving an inaccurate reading
  5. 5Poor connection at the sensor connector

How to diagnose it

Work through these in order before buying parts

  1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
  2. 2Inspect the engine coolant temperature (ECT) sensor connector and wiring (in the thermostat housing, cylinder head or intake manifold coolant passage). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
  3. 3Watch the engine coolant temperature (ECT) sensor reading on live data. After a cold soak it should match the outside temperature. With the engine warm it should rise steadily to about 85–105 °C (185–220 °F) and stay there.
  4. 4Compare the engine coolant temperature (ECT) sensor reading against related sensors and the real-world condition. If they disagree, find out which one is telling the truth before buying parts.
  5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
  6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

  • Fix the underlying problem the sensor is reporting, if real
  • Replace the engine coolant temperature (ECT) sensor if it reads wrong against a known-good reference

This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.