Mercury MerCruiser MCM 7.4L MPI User Manual

TROUBLE CODE DIAGNOSTICS - 7.4L MPI SERVICE MANUAL NUMBER 23
Page 5G-6 90-861326--1 MARCH 1999
Code 14 (3 of 3): Engine Coolant Temperature (ECT) Sensor Circuit
(Non-Scan) Low Temperature Indicated
ENGINE COOLANT TEMPERATURE SENSOR CHART
ECT Sensor
Temperature - to - Resistance Values (Approximate)
°F °C OHMS
210
160
100
70
40
20
0
-40
100
70
38
20
4
-7
-18
-40
185
450
1,800
3,400
7,500
13,500
25,000
100,700
Code 15 (1 of 3): Engine Coolant Temperature (ECT) Sensor Circuit
(Non-Scan) High Temperature Indicated
a
b
c
d
a-Engine Coolant Temperature (ECT) Sensor
b-To Map Sensor
c-Engine Coolant Temperature (ECT)
d-Sensor Ground
CIRCUIT DESCRIPTION:
The Engine Coolant Temperature (ECT) sensor uses a thermistor to control the signal
voltage to the ECM. The ECM applies 5 volts on CKT 410 to the sensor. When the engine
coolant is cold, the sensor (thermistor) resistance is high. As the engine coolant warms up,
the sensor resistance becomes less. see engine coolant temperature sensor chart under
“Diagnostic Aids.” At normal operating temperature 160°F-180°F (71°C-82°C), the voltage
will measure about 1.5-2.0 volts.
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Index

Mercury MerCruiser MCM 7.4L MPI Specifications

General

Brand	Mercury
Model	MerCruiser MCM 7.4L MPI
Category	Engine
Language	English