Dodge Dakota (R1). Manual - part 256
(2) Insert block heater assembly with element loop
pointing at twelve o’clock (Fig. 7).
(3) With block heater fully seated, tighten center
screw to 2 N·m (17 in. lbs.) torque.
(4) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(5) Start and warm the engine. Check 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 - 3.9L/5.2L/5.9L
The engine coolant temperature sensor is installed
into a water jacket at front of intake manifold near
rear of generator (Fig. 8).
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 cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(2) Disconnect electrical connector from sensor
(Fig. 8).
(3) Engines
with
air
conditioning:
When
removing the connector from sensor, do not pull
directly on wiring harness. Fabricate an L-shaped
hook tool from a coat hanger (approximately eight
inches long). Place the hook part of tool under the
connector for removal. The connector is snapped onto
the sensor. It is not equipped with a lock type tab.
(4) Remove sensor from intake manifold.
REMOVAL - 4.7L
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 ECT sensor is located near the front of the
intake manifold (Fig. 9).
(1) Partially drain cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(2) Disconnect electrical connector from ECT sen-
sor.
(3) Remove sensor from intake manifold.
Fig. 8 Engine Coolant Temperature Sensor—5.2L/
5.9L Engines—Typical
1 - GENERATOR
2 - A/C COMPRESSOR
3 - ENGINE COOLANT TEMPERATURE SENSOR
4 - ELEC. CONN.
7 - 36
ENGINE
AN
ENGINE BLOCK HEATER - 4.7L (Continued)