DTC 15

DTC 15 - Engine Coolant Temperature (ECT) Sensor Circuit (Low Temperature Indicated):

Engine Coolant Temperature (ECT) 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 88 to 106°C (190 to 222°F) the voltage will measure about .5 to 1.1 volts at the ECM.

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

1. DTC 15 will set if:
^ Engine running longer than 30 seconds.
^ Engine coolant temperature less than -33°C (-27°F).
2. This test simulates a DTC 14. If the ECM recognizes the low signal voltage, (high temperature) and Tech 1 scan tool reads 130°C or above, the ECM and wiring are OK.
3. This test will determine if CKT 410 is open. There should be 5 volts present at sensor connector if measured with a DVM.

Diagnostic Aids:

A Tech 1 scan tool reads engine temperature in degrees centigrade and degrees fahrenheit. After engine is started the temperature should rise steadily between 88°C (106°F) then stabilize when thermostat opens. The fan will turn "ON" at 106°C (222°F).

If DTC 21 is also set, check CKT 452 for faulty wiring or connections. Check terminals at sensor for good contact.

- Intermittent Malfunctions