P0117 AUDI Engine Coolant Temperature Circuit Low

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 circuit poor electrical connection
When is the code detected?
An excessively low voltage from the sensor is sent to ECM.
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P0117 AUDI 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.