P1118 Possible Causes
- Faulty Engine Coolant Temperature (ECT) sensor
- Low engine coolant level
- Engine Coolant Temperature (ECT) sensor harness is open or shorted
- Poor electrical connection in Engine Coolant Temperature (ECT) sensor circuit
- Faulty engine coolant thermostat
How is P1118 Code Repaired?
Begin by checking the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
Check Engine Light on (or service engine soon warning light)
P1118 Meaning
The Engine Coolant Temperature (ECT) sensor contains a semiconductor device that changes resistance based on temperature (a thermistor). The ECT sensor is mounted in the left bank cylinder head near the front of the engine. The ECT sensor has a signal circuit and a ground circuit. The PCM applies a voltage (approximately 5.0 volts) to the sensor signal circuit. The PCM monitors changes in this voltage caused by changes in the sensor’s resistance to determine the engine coolant temperature.
When the engine coolant is cold, the sensor’s (thermistor) resistance is high and the PCM signal voltage is only slightly lowered across the sensor to ground. The PCM detects a high signal voltage (low temperature). When the engine coolant is hot, the sensor resistance is low and the signal voltage is lowered further. This causes the PCM to detect a low signal voltage (high temperature).