Cooling

P0119 — Engine Coolant Temperature Sensor Circuit Intermittent

Severity: medium Drive with care, to a shop

What P0119 means

The engine control module reads the voltage from the engine coolant temperature (ECT) sensor to know how warm the engine is. P0119 is stored when that signal drops out, jumps around or doesn't match actual engine warm-up. The module uses this data to set fuel delivery, idle speed and cooling fan operation, so bad readings upset engine management.

Symptoms

  • Check Engine light is on
  • Temperature gauge flickers or jumps
  • Rough idle or hesitation on acceleration
  • Poor fuel economy
  • Cooling fan runs constantly or never turns on
  • Hard starting when hot or cold

Possible causes

  1. Failing ECT sensor with an erratic signal
  2. Loose, corroded or damaged sensor connector
  3. Chafed, open or shorted wiring, especially near the exhaust manifold
  4. Low coolant level or air pockets in the cooling system
  5. Faulty thermostat that prevents normal engine temperature
  6. Rarely, an ECM software or internal fault

How to diagnose

  1. Scan for codes and watch live coolant temperature data during warm-up
  2. Check the coolant level and make sure there is no air in the system
  3. Inspect the sensor connector for tight fit, corrosion and moisture
  4. Inspect the harness for chafing or heat damage, and wiggle it with the engine running while watching the data
  5. Measure sensor resistance cold and warm and compare with the factory specification
  6. Check the 5-volt reference and ground at the sensor connector
  7. Compare the scan tool reading with an infrared thermometer reading of the engine
  8. Test the thermostat to confirm the engine warms up and holds normal temperature

Common fixes

  • Replace the engine coolant temperature sensor
  • Repair the wiring or replace the connector and clean the terminals
  • Top up the coolant and bleed the air from the system
  • Replace a faulty thermostat
  • Update or replace the ECM if everything else checks out

Questions and answers

Can I drive with a P0119 code?

Briefly, if you watch the temperature gauge closely. False data can keep the fan from turning on and let the engine overheat, so don't put off the repair.

What most often causes P0119?

Usually the sensor itself or a poor connection in its connector or wiring. Inspect the connector and harness first, then check the coolant level.

Why does my temperature gauge jump around?

The gauge gets the same unstable signal the engine computer does. That points to a failing sensor or an unreliable connection in the circuit.

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.