Engine Coolant Temperature Sensor

WARNING: This page is about a different car, the 2009 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.

At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return).

When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.

The PCM uses inputs from the ECT sensor for the following calculations:

for engine coolant temperature gauge operation through the bus communications
Injector pulse-width
Spark-advance curves
ASD relay shut-down times
Idle Air Control (IAC) motor key-on steps
Pulse-width prime-shot during cranking
O2 sensor closed loop times
Purge solenoid on/off times
EGR solenoid on/off times (if equipped)
Leak Detection Pump operation (if equipped)
Radiator fan relay on/off times (if equipped)
Target idle speed