Code 21

Engine Coolant Temperature Sensor Circuit:

To test the Coolant Temperature Sensor, located in the intake manifold, proceed as follows.

Coolant Temperature Sensor:

1. Remove the Coolant Temperature Sensor from the intake manifold.

Coolant Temperature Sensor Test:

2. With the sensing portion of the Coolant Temperature Sensor immersed in hot water, check resistance between the two terminals. The sensor should be held with its threaded housing 3 mm (1/8in.) away from the surface of the hot water.

Standard Values
5.9k ohms at 32° F
2.5k ohms at 68° F
1.1k ohms at 104° F
0.3k ohms at 176° F


3. If the resistance deviates from the standard value, replace the sensor.

Coolant Temperature Sensor Connector Test:

NOTE: If the temperature of the engine coolant is known, then the sensor may be tested at the connector.