Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

COOLANT TEMPERATURE SENSOR DIAGNOSTIC CHART

Coolant Temperature Sensor Diagnostic Chart:

A faulty coolant temperature sensor will set code 21 in the on-board diagnostic system. Refer to the schematic diagram and test the sensor with the diagnostic chart.

Coolant Temperature Sensor Schematic:

CHECK ECU VOLTAGE
With ignition "ON," measure voltage between ECU connector terminal (B48)7 and ground. It should measure 0.6 - 4.5V.


CHECK COOLANT TEMPERATURE SENSOR

Coolant Temperature Sensor Testing:

Disconnect sensor connector and measure resistance between sensor terminals. It should read as follows:

Resistance: Temperature:
2.0 - 3.0K Ohms 20°C (68°F)
0.3 - 0.4K Ohms 80°C (176°F)


CHECK HARNESS BETWEEN ECU AND COOLANT SENSOR
1. Disconnect ECU and coolant sensor connectors.
2. Measure resistance between ECU and coolant sensor connectors as follows:

Connector & terminal: Resistance:
(B48)7 - (E7)1 0 Ohm
(B48)21 - (E7)2 0 Ohm

3. Measure resistance between coolant sensor terminals and ground as follows:

Connector & terminal: Resistance:
(E7)1 - Ground 1M Ohms min.
(E7)2 - Ground 1M Ohms min.