Possible causes

– Low engine coolant level
– Faulty Engine Coolant Temperature (ECT) sensor
– Faulty engine coolant thermostat
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

When is the code detected?

The Engine Control Module (ECM) detected an erratic signal from the engine Coolant Temperature (ECT) sensor during the system monitor test

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0119 MAZDA Description

The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.