Cooling

P0116 — Coolant Temperature Sensor Range/Performance Problem

Severity: medium Drive with care, to a shop

What P0116 means

The engine control module compares the coolant temperature sensor signal with how the engine should warm up. If the reading rises too slowly, stalls, or jumps around, it sets P0116. The cause may be the sensor or its circuit, or a real cooling system problem.

Symptoms

  • Check Engine Light is on
  • Temperature gauge reads wrong or fluctuates
  • Hard starting or rough idle when cold
  • Reduced fuel economy
  • Long warm-up and weak cabin heat
  • Cooling fan runs at the wrong time

Possible causes

  1. Faulty engine coolant temperature (ECT) sensor
  2. Damaged wiring or corroded connector in the ECT circuit
  3. Thermostat stuck open or closed
  4. Low coolant level or air trapped in the cooling system
  5. Poor ground or ECM fault (rare)

How to diagnose

  1. Scan for codes and freeze-frame data, and look for other temperature or fan codes
  2. Check coolant level and condition with the engine cold
  3. Inspect the sensor connector and harness for damage, moisture and corrosion
  4. Compare scan tool ECT reading to actual temperature with an infrared thermometer
  5. Measure sensor resistance cold and hot against factory specs
  6. Confirm the engine reaches normal temperature and the upper hose heats up on time (thermostat check)
  7. Check fan operation and bleed any air from the system

Common fixes

  • Replace the ECT sensor
  • Repair wiring or replace a damaged connector
  • Replace the thermostat
  • Top off coolant and bleed the cooling system

Questions and answers

What does P0116 mean?

The coolant temperature sensor signal doesn't match what the ECM expects during warm-up. The sensor, its wiring, or the thermostat may be at fault.

Can I drive with P0116?

Briefly and carefully, watching the temperature gauge, but don't put the repair off. Wrong data can hurt fuel economy and cooling control.

Is the thermostat a common cause?

Yes. A thermostat stuck open keeps the engine from warming properly, which triggers this code. Check warm-up behavior before replacing the sensor.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.