Dodge Durango

 Service Manual

Fuel System » Fuel injection system » Description and operation
Engine coolant temperature sensor-pcm input

DESCRIPTION

The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.

The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.

OPERATION

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 airfuel 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 CCD or PCI (J1850) 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

Powertrain control module (pcm)

Modes of operation

Automatic shutdown (asd) relay sense-pcm input

Battery voltage-pcm input

Brake switch-pcm input

Engine coolant temperature sensor-pcm input

Five volt sensor supplies-primary and secondary

Ignition circuit sense-pcm input

Intake manifold air temperature sensor-pcm input

Manifold absolute pressure (map) sensor-pcm input

Oil pressure sensor-pcm input

Oxygen sensor (o2s)-pcm input

Power grounds

Power steering pressure switch- pcm input

Sensor return-pcm input

Throttle position sensor (tps)-pcm input

Vehicle speed and distance-pcm input

Auto shutdown (asd) relay-pcm output

Ccd bus (+/-) circuits-pcm outputs

Data link connector-pcm input and output

Fuel injectors-pcm output

Fuel pump relay-pcm output

Idle air control (iac) motor-pcm output

Oxygen sensor heater relays-pcm output

Radiator cooling fan relay-pcm output

Throttle body