Code 22, Coolant Temp Sensor (Cts) CKT, Open Or Shorted CKT: Notes

The Coolant Temperature Sensor (CTS) uses a thermistor to control signal voltage to ECM. ECM applies voltage on White wire to the sensor. When engine is cold, thermistor resistance is high. ECM will sense high signal voltage. As engine warms up, thermistor resistance decreases. ECM will sense low signal voltage. When engine reaches normal operating temperature, 176-203°F (80-95°C), signal voltage will be approximately 1.5-2.0 volts at ECM.

1. Verifies if 4-5 volts is present at CTS connector.
2. Checks ground side of CTS circuit.
3. Determines if problem is caused by an open Brown wire or faulty ECM. Ensure ECM connectors fit properly.
4. Determines if circuit or ECM is the problem. Ensure ECM connectors fit properly.