Code 22, Engine Coolant Temp Sensor, Open Or Shorted CKT: Notes

Engine Coolant Temperature (ECT) sensor is a thermistor 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 and when engine is warm, PCM receives a low voltage input.

Code 22 will set if voltage input at PCM indicates either a very low or very high engine coolant temperature for at least .5 second.

1. Checks for open or short to ground in White wire between PCM and ECT sensor or a faulty PCM.
2. Checks for open in Brown wire between PCM and ECT sensor or a faulty PCM.
3. Determines if problem is a faulty ECT sensor or PCM.