Installation; Engine Coolant Temperature Sensor; Description; Operation - Dodge dakota 2002 Service Manual

7 - 44 ENGINE
ENGINE BLOCK HEATER - 5.9L DIESEL (Continued)
(4) Using a suitable size socket, loosen and remove
the block heater element (Fig. 10).
Fig. 10 Block Heater-Diesel Engine
1 - BLOCK HEATER

INSTALLATION

(1) Clean and inspect the threads in the cylinder
block.
(2) Coat heater element threads with Mopar
Thread Sealer with Teflon.
(3) Screw block heater into cylinder block and
tighten to 43 N·m (32 ft. lbs.).
(4) Connect block heater cord and tighten retain-
ing cap.
(5) Fill cooling system with recommended coolant
(Refer to 7 - COOLING - STANDARD PROCE-
DURE).
(6) Start and warm the engine.
(7) Check block heater for leaks.
ENGINE COOLANT
TEMPERATURE SENSOR

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, resis-
tance (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 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 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

REMOVAL

3.7L V-6
The Engine Coolant Temperature (ECT) sensor on
the 3.7L engine is installed into a water jacket at
front of intake manifold near rear of generator (Fig.
11).
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE COOLANT TEMPERATURE SENSOR.
(1) Partially drain the cooling system.
(2) Disconnect the electrical connector from the
sensor.
(3) Remove the sensor from the intake manifold.
4.7L V-8
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE ENGINE COOLANT TEMPERATURE (ECT)
SENSOR.
The Engine Coolant Temperature (ECT) sensor on
the 4.7L V-8 engine is located near the front of the
intake manifold (Fig. 12).
(1) Partially drain the cooling system. Refer to 7,
COOLING.
(2) Disconnect the electrical connector from the
ECT sensor.
(3) Remove the sensor from the intake manifold.
DR