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MEFI 4 - PCM
General Description
Visual and Physical Inspection
Important: This visual and physical inspection is
very important. Perform this inspection carefully and
thoroughly. Perform a careful visual and physical
inspection when performing any diagnostic procedure.
This can often lead to repairing a problem without further
steps. Use the following guidelines when performing a
visual and physical inspection:
• Inspect all vacuum hoses for the following
conditions:
– Correct routing
– Pinches
– Cuts
– Disconnects
• Inspect all wires in the engine compartment for the
following conditions:
– Proper connections
– Burned or chafed spots
– Pinched wires
– Contact with sharp edges
– Contact with hot exhaust manifolds
Basic Knowledge and Tools Required
To use this manual most effectively, a general
understanding of basic electrical circuits and circuit
testing tools is required. You should be familiar with wiring
diagrams, the meaning of voltage, ohms, amps and the
basic theories of electricity. You should also understand
what happens if a circuit becomes open, shorted to ground
or shorted to voltage.
To perform system diagnostics, several special tools and
equipment are required. Please become acquainted with
the tools and their use before attempting to diagnose the
system. Special tools that are required for system service
are illustrated in this section.
Electrostatic Discharge Damage
Electronic components used in control systems are often
designed to carry very low voltage, and are very susceptible
to damage caused by electrostatic discharge. It is possible
for less than 100 volts of static electricity to cause damage
to some electronic components. By comparison, it takes
as much as 4,000 volts for a person to feel the zap of
a static discharge.
There are several ways a person can become statically
charged. The most common methods of charging are by
friction and by induction. An example of charging by friction
is a person sliding across a seat, in which a charge of as
much as 25,000 volts can build up. Charging by induction
occurs when a person with well insulated shoes stands
near a highly charged object and momentarily touches
ground. Charges of the same polarity are drained off,
leaving the person highly charged with the opposite
polarity. Static charges of either type can cause damage.
Therefore, it is important to use care when handling and
testing electronic components.
Engine Wiring
When it is necessary to move any of the wiring, whether
to lift wires away from their harnesses or move harnesses
to reach some component, take care that all wiring is
replaced in its original position and all harnesses are
routed correctly. If clips or retainers break, replace them.
Electrical problems can result from wiring or harnesses
becoming loose and moving from their original positions,
or from being rerouted.
Engine Control Module (ECM) Self-
Diagnostics
The Engine Control Module (ECM) performs a continuous
self-diagnosis on certain control functions. This diagnostic
capability is complemented by the diagnostic procedures
contained in this manual. The ECM’s language for
communicating the source of a malfunction is a system of
Diagnostic Trouble Codes (DTC’s). The DTC’s are two digit
numbers that can range from 12 to 81. When a malfunction
is detected by the ECM, a DTC is set and the Malfunction
Indicator Lamp (MIL) is illuminated.
Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) is part of the Marine
Diagnostic Trouble Code (MDTC) tool, or it can be a dash
mounted warning light on some boat models.
•
If present, it informs the operator that a problem has
occurred and that the boat should be taken for service
as soon as reasonably possible.
•
It displays DTC’s stored by the ECM which help the
technician diagnose system problems.
As a bulb and system check, the light will come “ON” with
the key “ON,” engine “OFF.” When the engine is started,
the light will turn “OFF.” If the light remains “ON,” the
self-diagnostic system has detected a problem. If the
problem goes away, the light may go out, but a DTC will
remain stored in the ECM.
When the light remains “ON” while the engine is running,
or when a malfunction is suspected due to a driveability
problem, the MEFI “On-Board Diagnostic (OBD) System
Check” must be performed as the fi rst step. These checks
will expose malfunctions which may not be detected if other
diagnostics are performed prematurely.
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