Ect (Engine Coolant Temperature) Sensor - Mercury MerCruiser D2.8L D-Tronic Service Manual

EDI DIAGNOSIS

ECT (Engine Coolant Temperature) Sensor

Scan Code:
Blink Code:
Malfunction Indicator Lamp:
CIRCUIT DESCRIPTION:
The ECT (Engine Coolant Temperature) Sensor is a thermistor (a resistor which changes
value based on temperature) immersed in the engine coolant stream. Low coolant
temperature produces a high resistance, while high temperature causes low resistance.
The ECM supplies a 5 volt signal to the ECT through a resistor in the ECM and measures
the voltage. The voltage will be high when the engine is cold, and low when the engine is
hot. By measuring the voltage, the ECM knows the engine coolant temperature. Engine
coolant temperature affects most systems the ECM controls. The voltage received at the
ECM will determine operation of the fuel timing solenoid and glow plug relays.
A failure in the ECT circuit should set Scan Code P0115. Remember, this code indicates a
failure in the coolant temperature sensor circuit, so proper use of the test description
information will lead to either repairing a wiring problem or replacing the sensor.
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Page 5E-22
b
a
1
14
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2
a - ECT Sensor
b - ECT Connector
c - ECT Signal
d - 5 Volt Reference Signal
e - Sensor Ground
f - To Injection Pump
CKT PIN
Engine Coolant Temperature Sensor Signal
Sensor Ground (–)
P0115
1113
ON
WHT/BRN 14
33
BRN/PUR
f
NAME
90-860074--1 FEBRUARY 2002
SERVICE MANUAL NUMBER 22
c
d
e
75341