DTC 14

Code 14 "Coolant Temperature Sensor":

Wiring Diagram - Coolant Temperature Sensor:

CODE 14

COOLANT TEMPERATURE SENSOR CIRCUIT (HIGH TEMPERATURE INDICATED)


Circuit Description:

The coolant temperature sensor 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 180 degrees F to 203 F (85 C to 95 C) the voltage will measure about 1.5 to 2.0 volts.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 14 will set if. O2 Signal voltage indicates a coolant temperature above 167 degrees C (333 F) for 90 seconds or more.

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

Diagnostic Aids:

"Scan" tool displays engine temperature in degrees celsius. After engine is started, the temperature should rise steadily to about 90 degrees C, then stabilize when thermostat opens. An intermittent may be caused by a rubbed through wire insulation.


Check for:
Damaged Harness - Inspect ECM harness for damage or rubbed through insulation which could cause CKT 410 to short to ground or to a ground circuit such as CKT 452.

Intermittent Test - If connections and harness check OK, "Scan" 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.