DTC 15

DIAGNOSTIC CHART





WIRING DIAGRAM





SENSOR VALUES CHART

INSPECTION PROCEDURE

Circuit Description:
The ECT Sensor uses a thermistor to control the signal voltage to the Engine Control Module (ECM). The ECM applies a voltage on CKT C10 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 95°C) the voltage will measure about 1.5 to 2.0 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.
- ECT less than -33°C (-27°F), for 3 seconds.
2. This test simulates a DTC 14. If the ECM recognizes the low signal voltage, (high temperature) and "Scan" reads 135°C (275°F) or above, the ECM and wiring are OK.
3. This test will determine if CKT C10 is open. There should be 5 volts present at sensor connector if measured with a DVM.

Diagnostic Aids:
A "Scan" tool reads engine temperature in degrees centigrade. After engine is started the temperature should rise steadily to about 90°C then stabilize when thermostat opens.
If DTC 21 is also set, check CKT D2 for faulty wiring or connections. Check terminals at sensor for good contact.
Refer to "Intermittents" in "Symptoms".