P0116

What it means

P0116 is the generic code for an engine coolant temperature sensor 1 signal that is out of range or does not make sense compared with other data. The engine control unit saw a reading that did not match what it expected, for example the temperature not rising as the engine warmed up, sticking at a value, or disagreeing with intake air temperature after a long cold soak. It does not by itself say whether the sensor, the wiring or the cooling system is at fault.

Symptoms

• Engine management warning light on
• Hard or extended cranking when starting, particularly when warm
• Cooling fans running constantly or at odd times
• Poor fuel economy or rough running on a cold or warm engine
• Temperature gauge reading erratic, stuck or slow to rise
• Black smoke or a rich smell on start-up

Possible causes

• Faulty or drifting coolant temperature sensorlikely
• Thermostat stuck open, so the engine warms up too slowly or does not reach normal temperaturelikely
• Corroded, loose or damaged sensor connector or terminalslikely
• Wiring fault such as chafing, high resistance or a short on the signal or reference circuitpossible
• Low coolant level or air trapped in the cooling system giving a false reading at the sensorpossible
• Fault in a second coolant sensor or shared sensor circuit, depending on the vehicle layoutrare
• Engine control unit fault or outdated calibration where the manufacturer has identified onerare

How to diagnose

1. Read the stored codes and freeze frame data, noting coolant temperature, engine load and run time when the code set, and check for other temperature or circuit codes
2. Check the coolant level when cold and look for leaks, air pockets or signs of poor maintenance
3. Inspect the sensor connector and wiring for corrosion, damage, bent pins or water ingress
4. With the engine fully cold, compare coolant temperature with intake air temperature on live data; they should be close after a long soak
5. Watch coolant temperature on live data from a cold start and check it rises smoothly to normal operating temperature without jumps or stalling
6. Compare the scan tool reading with an independent temperature measurement of the engine, such as an infrared thermometer on the housing
7. Check the thermostat operation: the upper hose should stay cool then warm up as the engine reaches opening temperature
8. Measure sensor resistance against the manufacturer's temperature table and check the reference voltage, signal and ground circuits for faults; the values depend on the model

How to fix

• Replace the coolant temperature sensor if its readings are out of specification or erratic
• Replace a thermostat that is stuck open or opening at the wrong temperature
• Repair or replace damaged wiring, terminals or the connector, and clean up any corrosion
• Top up and bleed the cooling system correctly, and fix any leak found
• Apply a manufacturer calibration update only where a known software issue applies to the vehicle
• After repair, clear the codes and complete a drive cycle to confirm the fault does not return

Can I keep driving?

Nearby codes

• P0115GenericEngine Coolant Temperature Sensor 1 Circuit
• P0117GenericEngine Coolant Temperature Sensor 1 Circuit Low