DTC P0118: Engine Coolant Temperature Sensor Circuit, High Input: Condition

WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set if input voltage from Engine Coolant Temperature (ECT) sensor is more than 4.94 volts. This is a continuous monitor. MIL is illuminated when PCM detects malfunction during first drive cycle. Possible causes

ECT sensor malfunction.
Open circuit between ECT sensor and PCM.
PCM malfunction.