Possible causes

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

Symptoms

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

P1117 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.