Code 14 (Standard Emissions) - Engine Coolant Temperature Sensor, Low Temperature Indicated: Notes

Engine Coolant Temperature (ECT) sensor is a thermistor in series with a fixed resistor in ECM. ECM applies 5 volts to sensor. ECM monitors voltage across ECT sensor and converts it into a temperature reading. When engine is cold, ECT sensor resistance is high. When engine is warm, ECT sensor resistance is low. Therefore, when engine is cold, ECM receives a high voltage input and when engine is warm, ECM receives a low voltage input. Code 14 will set if voltage input at ECM indicates a coolant temperature of less than -54°F (-48°C) for at least 3 seconds.

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