P0116: Engine Coolant Temperature Sensor 1 Circuit Range/Performance

What does P0116 mean?

The ECT sensor tells the engine computer how warm the engine is. The computer uses it for fuel mixture, idle speed, closed loop entry and often the cooling fans. P0116 means the reading is out of the expected range for the conditions rather than a simple open or short.

YourMechanic advises diagnosing other coolant temperature codes such as P0117, P0118 or P0125 first, and checking the thermostat, because a thermostat that opens too early can also make the reading look wrong.

Common symptoms

• Check engine light on
• Hard starting or rough running when cold
• Lower fuel economy
• In some cases no obvious symptoms

Common causes

The causes below are the ones commonly seen with P0116. The actual cause can vary by vehicle, engine and mileage, so treat this list as a starting point, not a diagnosis.

• A faulty engine coolant temperature sensor
• Damaged wiring or a poor connection in the ECT sensor circuit
• Old or contaminated coolant affecting the sensor (listed by RepairPal)
• A thermostat problem that changes how quickly the engine warms up (listed by YourMechanic)

What to check with a scanner

• After the car has sat overnight, compare coolant temperature and intake air temperature in Live data. They should be close.
• Start the engine and watch the coolant temperature rise smoothly to normal operating temperature.
• Check the coolant level and condition with the engine cold.
• Note any other coolant temperature or thermostat codes and diagnose those first.

How to read and clear P0116 with OBD Master Pro

1. Plug in your adapter. Connect a generic ELM327 (or ELM329) OBD2 adapter to the diagnostic port, usually under the dashboard on the driver's side. Bluetooth Classic, Bluetooth LE, Wi-Fi and USB OTG adapters are supported.
2. Switch the ignition on. Turn the key to ON or start the engine, depending on your car.
3. Connect in OBD Master Pro. Open the app, go to Connection and pick your adapter. Classic Bluetooth adapters connect from the Bluetooth tab, Bluetooth LE adapters from the BLE tab with no pairing needed. Use the generic OBD2 / EOBD profile or your car's brand profile.
4. Read the codes. Open the fault codes screen to see stored, pending and permanent codes. Confirm P0116 is listed and note any other codes, since they often explain the cause.
5. Check the details. Look at freeze frame data, Live data and, where your car supports it, Mode 06 test results (see the checks above).
6. Fix, then clear. After the repair, clear the codes to turn off the check engine light. Clearing also resets the emissions readiness monitors, so drive normally and check the readiness screen before any inspection. Permanent codes cannot be erased with a scan tool; they clear on their own once the car's self test passes.

Tip: you can also look up P0116 and other codes in the app's DTC search without connecting to a car. If your adapter will not connect, use Connection > Share connection log and email it to support. Many cheap ELM327 clones only handle basic engine OBD2, which is all you need for P0116.

When to see a mechanic

Get professional help if any of these apply:

• The temperature gauge reads high or the engine overheats (stop driving)
• The coolant reading jumps or stays cold while the engine is warm
• Coolant is low or leaking

If you are unsure, a qualified technician can confirm the cause with tests such as smoke testing, pressure testing or scope readings. Clearing a code does not repair the fault.

Related trouble codes

See all OBD2 trouble code guides

Related guides

Check engine light on: what to do · How to read an OBD2 code (P, B, C, U) · Stored, pending and permanent codes and freeze frame · OBD2 readiness monitors explained · OBD2 glossary · OBD2 by car brand