Removal; Installation; Engine Coolant Temperature Sensor; Description - Chrysler PT Cruiser Service & Repair Manual

PT
ENGINE BLOCK HEATER (Continued)
Fig. 20 Power Cord
1 - STRAP
2 - CONNECTOR
3 - POWER CORD

DIAGNOSIS AND TESTING

ENGINE BLOCK HEATER
If heater unit does not operate (Fig. 19), possible
causes can be either the power cord or the heater ele-
ment. Test the power cord for continuity with a 110-
volt voltmeter or 110-volt test light. Test heater
element continuity with an ohmmeter or a 12-volt
test light.
CAUTION: To prevent damage, the power cord (Fig.
20)must be secured in its retainer clips and away
from any components that may cause abrasion or
damage, such as linkages, exhaust components, etc.

REMOVAL

(1) Drain the cooling system (Refer to 7 - COOL-
ING/ENGINE - STANDARD PROCEDURE - DRAIN-
ING COOLING SYSTEM).
(2) Detach power cord plug from heater (Fig. 19).
(3) Loosen screw in center of heater. Remove
heater assembly (Fig. 19).
(4) If required, remove power cord (Fig. 20).

INSTALLATION

(1) Thoroughly clean core hole and heater seat.
(2) Insert heater assembly with element loop posi-
tioned upward (Fig. 19).
(3) With heater seated, tighten center screw
securely to assure a positive seal.
(4) If removed, install power cord (Fig. 20).
NOTE: Ensure power cord is properly routed and
secured with straps.
ENGINE - 2.0/2.4L DOHC
(5) Connect power cord to block heater (Fig. 19).
(6) Fill cooling system (Refer to 7 - COOLING/EN-
GINE - STANDARD PROCEDURE - FILLING
COOLING SYSTEM).
ENGINE COOLANT
TEMPERATURE SENSOR

DESCRIPTION

The engine coolant temperature (ECT) sensor
threads into the thermostat housing just below the
coolant outlet connector (Fig. 21) or (Fig. 22). New
sensors have sealant applied to the threads.
The ECT Sensor is a Negative Thermal Coefficient
(NTC) Sensor. The resistance of the ECT Sensor
changes as coolant temperature changes. This results
in different input voltages to the PCM. The PCM also
uses the ECT Sensor input to operate the radiator
cooling fan(s), and send a message over the PCI bus
to the instrument cluster for temperature gauge

operation.

Fig. 21 Engine Coolant Temperature Sensor

1 - ENGINE COOLANT TEMPERATURE SENSOR

OPERATION
The ECT sensor provides an input to the PCM. As
temperature increases, resistance of the sensor
decreases. As coolant temperature varies, the ECT
sensor resistance changes resulting in a different
voltage value at the PCM ECT sensor signal circuit.
The ECT sensor provides input for various PCM
operations. The PCM uses the input to control air-
fuel mixture, timing, and radiator fan on/off times.
The PCM uses ECT sensor input to send messages
over the PCI bus for temperature gauge operation.
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