MULTI-PORT FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
SERVICE MANUAL NUMBER 23
90-861326--1 MARCH 1999 Page 5B-7
Abbreviations (Continued)
RAM Random Access Memory
REF HI Reference High
REF LO Reference Low
ROM Read Only Memory
SLV Slave
SW Switch
TACH Tachometer
TERM Terminal
TP Throttle Position
V Volts
VAC Vacuum
WOT Wide Open Throttle
in-hg Inches Of Mercury
ECM Self-Diagnostics
The ECM performs a continual 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
codes. The codes are two digit numbers that can range from 12 to 52. When a malfunction
is detected by the ECM, a code is set and the Malfunction Indicator Lamp is illuminated.
Diagnostic Code Tool With Malfunction Indicator Lamp
There are various manufacturers of Diagnostic Code Tools. Most tools are equipped with
a Malfunction Indicator Lamp (MIL).
• It informs the service technician that a problem has occurred and that the vessel is in
need of service as soon as reasonably possible.
• It displays codes stored by the ECM which help the technician diagnose system
problems.
As a bulb and system check, the lamp will come ON with the key on and the engine not
running. When the engine is started, the light will turn OFF. If the lamp remains ON, the
self-diagnostic system has detected a problem. If the problem goes away, the light will go
out in most cases after ten seconds, but a code will remain stored in the ECM.
When the lamp remains ON while the engine is running, or when a malfunction is suspected
due to a driveability problem, “EFI Diagnostic Circuit Check” must be performed. These
checks will expose malfunctions which may not be detected if other diagnostics are
performed prematurely.
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