DTC 14

Chart - Code 14 Coolant Sensor Circuit (Signal Voltage Low):

Wiring Diagram for Coolant Sensor Circuit.:

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 Electronic Control Module (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 (85 to 95 Degrees 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 the signal voltage indicates a coolant temperature above 135 Degrees C (275 Degrees F) for calibrated time.
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 temp. in degrees centigrade. 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 poor connection, rubbed through wire insulation or a wire broken inside the insulation.


Check For:
Poor Connection or Damaged Harness Inspect ECM harness connectors for backed out terminals "ClO" or "Dl2", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

Intermittent Test. lf connections and harness checks out 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.