P0116: Engine Coolant Temperature Sensor 1 Circuit Range/Performance
The coolant temperature reading is out of line with what the engine computer expects, such as not warming up as it should.
What P0116 means
P0116 is a performance code, not a broken wire code. The engine computer is checking whether the coolant temperature reading behaves the way it should. For example, it expects the temperature to rise at a certain rate after a cold start, and it compares the reading to other sensors such as intake air temperature. If the reading stays flat, jumps or does not agree, it sets P0116. RepairPal lists a defective sensor, rusty coolant and corroded wiring as common causes. A thermostat stuck open can also confuse the test because the engine truly warms up too slowly. Shops look at the warm up curve on a scan tool, check the sensor against an infrared thermometer, test resistance at known temperatures, and inspect coolant condition. Because the coolant reading affects fueling and fan control, a bad sensor can cause poor mileage and hard starts. A real cooling problem behind it can cause overheating, so do not ignore a temperature gauge that acts strangely.
Common symptoms
- Check engine light on
- Temperature gauge stays low or jumps around
- Poor fuel economy
- Hard starting
- Heater slow to warm up
Most common causes
- Faulty ECT sensor that reads wrong but is not fully dead
- Thermostat stuck open
- Low coolant level or air pocket
- Rusty or contaminated coolant
- Corroded connector or wiring
What to check yourself first
Check coolant level when cold and look for leaks. Drive until fully warm and compare the scan tool coolant reading to an infrared thermometer pointed at the thermostat housing. If the engine never gets warm and the heater is weak, the thermostat may be stuck open.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace engine coolant temperature sensor | $499-$585 | When the sensor reading does not match a known good thermometer. |
| Replace thermostat | $616-$716 | If the engine actually runs too cool because the thermostat sticks open. |
| Coolant drain and refill | $440-$512 | Rusty or old coolant can cause bad readings and needs flushing. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For resistance in the wiring or connector. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0115 Engine Coolant Temperature Sensor 1 Circuit
- P0117 Engine Coolant Temperature Sensor 1 Circuit Low
- P0118 Engine Coolant Temperature Sensor 1 Circuit High
- P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
- P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control