DTC 14

Coolant Temperature Sensor (CTS) Circuit:

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

As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature (85°C to 95°C), the voltage will measure about 1.5 to 2.0 volts.

Code 14 will set if:

^ Engine run time is greater than 10 seconds.
^ CTS Signal voltage indicates a coolant temperature above 140°C (284°F) for .4 second.

Code 14 Coolant Temperature Sensor Diagnostic Chart:

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

1. Determines if conditions necessary to set Code 14 exist.

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


Diagnostic Aids:
Tech 1 displays engine temperature in degrees. After engine is started, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens.

An intermittent may be caused by rubbed through wire insulation.

Check For:

^ CKT 410 for a short to ground.

^ Intermittent Test - With Tech 1, monitor coolant temperature while moving related connectors and wiring harness. If the failure is induced, the "coolant temperature" display will change. This may help to isolate the location of the malfunction.

^ Shifted Sensor - The "Temperature To Resistance Value" scale may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor, which may result in driveability complaints.