Code 22, Coolant Temperature Sensor Circuit Open: Notes

OR SHORTED CIRCUIT

The Coolant Temperature Sensor (CTS) uses a thermistor to control signal voltage to the ECM. The ECM applies voltage on White wire to the sensor. When engine is cold, thermistor resistance is high, this means the ECM will see high signal voltage. As engine warms, thermistor resistance is less, this means the ECM will see low signal voltage. When engine reaches normal operating temperature, signal voltage will be approximately 1.5-2.0 volts at the ECM.

1. This verifies that 4-5 volts is present at CTS connector.
2. This checks ground side of CTS circuit.
3. This determines if problem is caused by an open Brown wire or the ECM. Ensure ECM connectors properly fit.
4. This determines if circuit or ECM is the problem. Ensure to check ECM connectors for proper fit.