DTC 14

Code 14 Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The coolant temperature sensor uses a thermistor to control the signal voltage at the ECM. The ECM applies a voltage on circuit 410 to the sensor. When the engine is cold the sensor (thermistor) resistance is high, therefore the ECM will see high signal voltage high.

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.

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 14 will set if:

^ Engine run time is 10 seconds or more.
^ Signal voltage indicates a coolant temperature above 140°C (284°F) for 0.4 seconds.

2. This test will determine if circuit 410 is shorted to ground which will cause the conditions for Code 14. If a code 14 is set, the ECM will use a default coolant temperature value of 49°C (120°F) for fuel control. Scan tool will read actual value not default value.

DIAGNOSTIC AIDS:

^ "Scan" tool displays engine temperature in degrees Celsius. After engine is started, the temperature should rise steadily to about 90°C (194°F), and 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:

^ 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.

^ Circuit 410 for a short to ground. Rubbed through wire insulation.