Code 15 - Coolant Sensor (Temperature Too Low): Notes
The coolant temperature sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage on circuit No. 410 to the sensor. When 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 the voltage will measure about 1.5-2.0 volts at the ECM.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
NOTE:
The "SCAN" tester displays engine temperature in degrees centigrade.
- Code 15 will set if the following conditions occur:
- Engine running longer than 30 seconds.
- Coolant temperature less than -22°F (-30°C), for 3 seconds.
- This test simulates a Code 14. If the ECM recognizes the low signal voltage, (high temperature) and the "SCAN" tester reads above 130°C, the ECM and wiring are okay.
- This test will determine if circuit No. 410 is open. There should be 5 volts present at sensor connector as measured with a digital volt/ohmmeter.