DTC 14

Coolant Temperature Sensor Circuit:

Circuit Description
The Coolant Temperature Sensor (CTS) uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage on CKT 410 to the sensor. When the engine is cold the sensor (thermistor) resistance is high therefore the ECM will see high signal voltage.

As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature 88 to 106°C (190 to 222°F) the voltage will measure about .5 to 1.1 volts.

Code 14 Diagnostic Chart:

Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Code 14 will set if:
^ Engine running longer than 6 seconds.
^ Signal voltage indicates a coolant temperature above 135°C (275°F).

2. This test will determine if CKT 410 is shorted to ground which will cause the conditions for Code 14.


Diagnostic Aids
Check harness routing for a potential short to ground in CKT 410. Tech 1 "Scan" tool displays engine temperature degrees centigrade and degrees fahrenheit. After engine is started, the temperature should rise steadily between 88-106°C (190-222°F) then stabilize when thermostat opens. The cooling fan should turn "ON at 106°C (222°F). - Intermittent Malfunctions