Jeep Grand Cherokee WK. Manual — part 209
5. Remove power cord from block heater.
6. Loosen screw at center of block heater. Remove
heater assembly.
INSTALLATION
3.7L ENGINE
1. Thoroughly clean core hole and heater seat.
2. Insert heater assembly with element loop posi-
tioned upward .
3. With heater seated, tighten center screw securely
to assure a positive seal.
CAUTION: To prevent damage, the power cord
must be secured in it’s retaining clips, and not
positioned so it could contact linkages or exhaust
manifold.
4. Connect power cord to heater.
5. Lower vehicle.
6. Fill cooling system (Refer to 7 - COOLING - STAN-
DARD PROCEDURE).
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ENGINE
WK
4.7L ENGINE
1. Thoroughly clean cylinder block core hole and
block heater seat.
2. Insert block heater assembly with element loop
pointing at twelve o’clock.
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.
SENSOR-ENGINE COOLANT TEMPERATURE
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 sen-
sor 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
WK
ENGINE
7 - 43
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.
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 sen-
sor.
3. Remove the sensor from the intake manifold.
4.7L ENGINE
WARNING: HOT, PRESSURIZED COOLANT CAN CAUSE INJURY BY SCALDING. COOLING SYSTEM MUST
BE PARTIALLY DRAINED BEFORE REMOVING THE ENGINE COOLANT TEMPERATURE (ECT) SENSOR.
REFER TO GROUP 7, COOLING.
The ECT sensor is located near the front of the intake manifold.
1. Partially drain cooling system. (Refer to 7 - COOLING - STANDARD PROCEDURE).
2. Disconnect electrical connector from ECT sensor.
3. Remove sensor from intake manifold.
7 - 44
ENGINE
WK
5.7L ENGINE
The Engine Coolant Temperature (ECT) sensor on the
5.7L engine is located under the air conditioning com-
pressor. It is installed into a water jacket at the front of
the cylinder block.
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 (Refer to 7 -
COOLING - STANDARD PROCEDURE).
2. Remove accessory drive belt (Refer to 7 - COOL-
ING/ACCESSORY
DRIVE/DRIVE
BELTS
-
REMOVAL).
3. Carefully unbolt air conditioning compressor from
front of engine. Do not disconnect any A/C hoses
from compressor. Temporarily support compressor
to gain access to ECT sensor. Refer to Heating
and Air Conditioning section for information.
4. Disconnect electrical connector from sensor.
5. Remove sensor from cylinder block.
WK
ENGINE
7 - 45
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