Code 22 (PRIZM) - Engine Coolant Temperature Sensor, Open Or Shorted Circuit: Notes

Engine Coolant Temperature (ECT) sensor is a thermistor in series with a fixed resistor in ECM. ECM applies 5 volts to sensor. ECM 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, ECM receives a high voltage input and when engine is warm, ECM receives a low voltage input. Code 22 will set if voltage input at ECM 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 ECM and ECT sensor or a faulty ECM.
2. Checks for open in Brown wire between ECM and ECT sensor or a faulty ECM.
3. Determines if problem is a faulty ECT sensor or ECM.