P0116Engine Coolant Temperature Sensor 1 Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The engine coolant temperature sensor 1 is an NTC thermistor: the control module feeds 5 V through a resistor, and as the coolant warms the resistance and signal voltage fall. Its value drives cold-start enrichment, idle speed, ignition timing, the radiator fan and the release of closed-loop mixture control. Some Ford engines measure cylinder head temperature instead and calculate a coolant value from it. P0116 is a plausibility fault: the signal is electrically valid but not believable. Most often it checks for a sensor stuck too warm. After a long soak (GM 8 h, Ford 6 h) coolant must be close to intake air temperature; GM fails it above about 19 °C difference without a detected block heater, Ford if it reads over 110 °C or sits at 79–110 °C. Ford diesels instead check whether coolant warms fast enough in frost. A sensor stuck warm suppresses cold-start enrichment and can defeat the thermostat monitor, which is why CARB requires this test. GM uses one or two trips depending on the engine.
- What you may notice
- Check engine light on
- Poor cold start (too little enrichment)
- Higher consumption or idle problems
- Often no noticeable symptoms
- Likely causes
- LikelySensor drifting and reading too warm (ageing, coolant ingress)
- PossibleCorrosion or contact resistance in connector or wiring
- PossibleBlock heater or preheater not detected
- RareComparison sensor (intake air, ambient) wrong
- RareControl module calibration
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €180
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.