1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16

Electronic Control Module
(ECM) and Sensors
THREE-WIRE SENSORS (MAP AND TP)
The following figure shows a schematic representa-
tion of a 3-wire sensor. All 3-wire sensors have a ref-
erence voltage, a ground and a variable “wiper.” The
lead coming off of the wiper will be the signal to the
Engine Control Module (ECM). As this wiper position
changes, the signal voltage returned to the computer
also changes.
General Description
The MerCruiser Electronic  Fuel Injection system  is
equipped with a computer that provides the operator
with state-of-the-art control of fuel and spark delivery.
Computers use voltage to send and receive informa-
tion.
Computers and Voltage Signals
Voltage is electrical pressure. Voltage does not flow
in circuits. Instead, voltage  causes current. Current
does the real work in electrical circuits. It is current,
the flow of  electrically charged particles,  that ener-
gizes solenoids, closes relays and lights lamps.
3-Wire
Sensor
Besides causing currents in circuits, voltage can be
used as a signal. Voltage signals can send informa-
tion by changing levels, changing waveform (shape),
or changing the speed at which  the signal switches
from one  level to  another. Computers  use voltage
signals to communicate with one another. The differ-
ent sections inside computers also use  voltage sig-
nals to communicate with each other.
TWO-WIRE SENSORS (ECT AND IAT)
The following figure is the schematic of a 2-wire type
sensor. This sensor is basically a variable resistor in
series with a fixed-known resistor within the comput-
er. By knowing the values of the input voltage and the
voltage drop across the known resistor, the value of
the variable resistor can be determined. The variable
resistors that are commonly used are called thermis-
tors. A thermistor’s  resistance varies inversely with
temperature.
There are two  kinds of voltage signals, analog  and
digital. Both of these are used in computer systems.
It’s important to understand  the difference between
them and the different ways they are used.
Analog Signals
An  analog   signal  is  continuously   variable.  This
means that the signal can be any voltage within a cer-
tain range. An  analog signal usually gives informa-
tionaboutaconditionthatchangescontinuouslyover
a certain  range. For  example, in a  marine engine,
temperature is usually provided by an analog signal.
There are two general types of sensors that produce
analog signals: the 3-wire and the 2-wire sensor.
2-Wire
Sensor
Index
5C-10 - ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY)
90-823224--2  796
Product Specification
CategoriesMercury MerCruiser Manuals
Tags,
Model Year1993, 1994, 1995, 1996, 1997
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CopyrightAttribution Non-commercial
(4 votes, average: 4.5 out of 5)
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1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16 SKU UPC Model
Nick on Aug 13, 2018. Exactly what I was looking for!

Hugely helpful service manual! Perfect. Thank you!


Sonthaya Traipug on May 04, 2018. Freelance Yachts Service

Manuals are all Important for Technician


Glenn on Dec 02, 2015. Nice

This book is invaluable if you do your own repairs. Great book.


Joseph on Oct 04, 2015. 1997 7.4l Bravo

Could not find a copy until a search brought me here.
Excellent print.
Thank you


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