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Home >> Geo >> 1996 >> Prizm Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0115 - Engine Coolant Temperature Sensor Circuit >> Circuit Description

Circuit Description

Engine Coolant Temperature (ECT) sensor is a thermistor (a variable resistor) in series with a fixed resistor in PCM. PCM applies 5 volts to sensor. PCM monitors voltage across ECT sensor and converts it into a temperature reading. When engine is cold, ECT sensor resistance is high. When engine is warm, ECT sensor resistance is low. Therefore, when engine is cold, PCM receives a high voltage input. When engine is warm, PCM receives a low voltage input. DTC P0115 will set when voltage input at PCM indicates either a very low or very high engine coolant temperature for at least 0.5 second.

NOTE: If DTCs P0105, P0110, P0115 and P0120 are set together, sensor ground circuit may be at fault.
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