PleasureCraft Engine Group 5.0L, Diagnostic Manual, Page: 7 / 337

5.0/5.7/6.0L/8.1L General Information 1 - 3
MEFI 4 - PCM
Figure 1-1 - Marine Data Link Connector (DLC)
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B
C
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MS 13554
DATA LINK CONNECTOR (DLC)
6-18-93
times. At the end of the DTC’s, the ECM will simply go
back and start over with fl ashing DTC 12.
Service Mode
When the DTC tool is installed at the DLC and “service
mode” or “ON” is selected, the system will enter what is
called the “Service Mode.” In this mode, the ECM will:
•
Display a DTC 12 by fl ashing the MIL, indicating that
the diagnostic system is working.
•
Display any stored DTC’s by fl ashing the MIL. Each
DTC will be fl ashed two times, then DTC 12 will be
fl ashed again.
Normal Mode
When the DTC tool is in the “normal mode” or “OFF,” it has
no affect on the engine operation.
MEFI On-Board Diagnostic (OBD) System
Check
After the visual/physical inspection, the “On-Board
Diagnostic (OBD) System Check” is the starting point for all
diagnostic procedures. Refer to Diagnosis section.
The correct procedure to diagnose a problem is to follow
two basic steps:
1. Are the on-board diagnostics working? This is
determined by performing the “On-Board Diagnostic
(OBD) System Check.” Since this is the starting point
for the diagnostic procedures, always begin here. If
the on-board diagnostics are not working, the OBD
system check will lead to a Diagnostic Procedure
in the Diagnosis section to correct the problem. If
the on-board diagnostics are working properly, the
next step is:
2. Is there a DTC stored? If a DTC is stored, go directly to
the number DTC procedure in the Diagnosis section.
This will determine if the fault is still present.
DLC Scan Tools
The ECM can communicate a variety of information through
the DLC. This data is transmitted at a high frequency which
requires a scan tool for interpretation.
With an understanding of the data which the scan tool
displays, and knowledge of the circuits involved, the scan
tool can be very useful in obtaining information which
would be more diffi cult or impossible to obtain with other
equipment.
A scan tool does not make the use of Diagnostic Procedures
unnecessary, nor do they indicate exactly where the
problem is in a par ticular circuit. Some Diagnostic
Procedures incorporate steps with the use of a scan
tool (scan diagnostics), or with the DTC tool (non-scan
diagnostics).
a hand-held diagnostic scanner, plugged into the DLC.
Once the DTC tool has been connected, and “service
mode” or “ON” selected, the ignition switch must be moved
to the key “ON,” engine “OFF” position. At this point, the
MIL should fl ash DTC 12 two times consecutively. This
would be the following flash sequence: “flash, pause,
fl ash-fl ash, long pause, fl ash, pause, fl ash-fl ash.” DTC 12
indicates that the ECM’s diagnostic system is operating.
If DTC 12 is not indicated, a problem is present within
the diagnostic system itself, and should be addressed
by consulting the “On-Board Diagnostic (OBD) System
Check” in the Diagnosis section.
Following the output of DTC 12, the MIL will indicate a
DTC two times if a DTC is present, or it will continue to
fl ash DTC 12. If more than one DTC has been stored in
the ECM’s memory, the DTC’s will be fl ashed out from the
lowest to the highest, with each DTC being fl ashed two
Intermittent Malfunction Indicator Lamp (MIL)
In the case of an “intermittent” problem, the Malfunction
Indicator Lamp (MIL) will light for 10 seconds, and then
go out. However, the corresponding DTC will be stored
in the memory of the ECM. When DTC’s are set by an
intermittent malfunction, they could be helpful in diagnosing
the system.
If an intermittent DTC is cleared, it may or may not reset. If
it is an intermittent failure, consult the “Diagnostic Aids” on
the facing page of the corresponding Diagnostic Procedure.
Symptoms section also covers the topic of “Intermittents.”
A physical inspection of the applicable sub-system most
often will resolve the problem.
Reading Diagnostic Trouble Codes (DTC’s)
The provision for communicating with the ECM is the Data
Link Connector (DLC) (Figure 1-1). It is part of the MEFI
engine wiring harness, and is a 10-pin connector, which
is electrically connected to the ECM. It is used in the
assembly plant to receive information in checking that the
engine is operating properly before it leaves the plant. The
DTC(s) stored in the ECM’s memory can be retrieved two
different ways. One way is with a Diagnostic Trouble Code
(DTC) tool. The other way is through a scan tool,