Code 14, Coolant Temp Sensor (Cts) CKT, Low Temp. Indicated: Notes

Coolant temperature sensor is a thermistor in series with a fixed resistor in ECM. ECM applies 5 volts to sensor. ECM monitors voltage across CTS and converts it into a temperature reading. When engine is cold, CTS resistance is high. When engine is warm, CTS resistance is low. Therefore, when engine is cold, ECM receives a high voltage input and when engine is hot, ECM receives a low voltage input.

Code 14 will set if the following condition is met for at least 3 seconds:

• Voltage input at ECM indicates a coolant temperature of less than -54°F (-48°C).
  NOTE: Test numbers refer to test numbers on diagnostic chart.

1. This test simulates Code 15. If ECM stores Code 15, ECM and its wiring is okay and CTS is faulty. If Code 14 resets, CTS is okay and wiring to ECM or ECM is faulty.
2. This test determines whether there is an open in the Gray/White or Light Green/Black wire, a short to B+ in the Gray/White wire or a faulty ECM.