DTC 14

DTC 14 - Coolant Temperature (ECT) Sensor Circuit (High Temp):

Coolant Temperature Sensor Wiring Circuit:

Circuit Description:

The Engine Coolant Temperature (ECT) 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 (85°C to 100°C/185°F to 212°F), the ECT signal will measure about 1.5 to 2.0 volts.

DTC 14 will set if:

^ Engine run time 10 seconds or more.
^ ECT sensor voltage indicates an engine coolant temperature above 145°C (293°F) for .4 second.

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

1. This will determine if the ECT sensor is indicating a high temperature to the ECM.
2. This test will determine if CKT 410 is shorted to ground which will cause the conditions for DTC 14.

NOTICE: If DTC 14 is set, the ECM will use a fail-soft engine coolant temperature of 32°C (120°F) for fuel control. The Tech 1 will continue to display actual sensor value.

Diagnostic Aids:

The Tech 1 displays engine coolant temperature in degrees. After the engine is started, engine coolant temperature should rise steadily to about 90°C (194°F) 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 rubbed through wire insulation, damaged connections, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
^ Intermittent Test. If connections and harness check OK, scan coolant temperature while moving related connectors and wiring harness. If the failure is induced, the engine 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 ECT sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor, which may result in driveability complaints.