GENERAL SYSTEM DIAGNOSTICS
SERVICE MANUAL NUMBER 23
Diagnostic Circuit Check
The Diagnostic Circuit Check is an organized approach to identifying a problem created by
an electronic engine control system malfunction. It must be the starting point for any drive-
ability complaint diagnosis because it directs the service technician to the next logical step
in diagnosing the complaint.
NOTE: A scan tool that displays faulty data should not be used, and the problem should be
reported to the manufacturer. The use of a faulty scan tool can result in misdiagnosis and
unnecessary parts replacement.
The scan tool data listed in the table may be used for comparison. After completing the diag-
nostic circuit check and finding the on-board diagnostics functioning properly and no trouble
codes displayed. The “Typical Data Values” are an average of display values recorded from
normally operating vessels and are intended to represent what a normally functioning sys-
tem would typically display.
Only the parameters listed below are used in this manual for diagnosing. If a scan reads
other parameters, the values are not recommended for use in diagnosing. If all values are
within the range illustrated, refer to “Troubleshooting.”
Scan Tool Normal Specifications (Idle / Warm Engine / Closed Throttle /
Neutral)
SCAN POSITION
UNITS DISPLAYED
TYPICAL DATA VALUE
600-700 RPM
RPM
RPM
RPM
Desired RPM
Coolant Temp.
600 RPM
° F(° C)
° F (° C)
150-170° F (66-77° C)
Varies with Ambient Tempera-
ture
Manifold Air Temp.
Throttle Position
Throttle Angle
Volts
.4 to .8 Volts
0-1%
0-100 %
1-3
(Depends on Vacuum and
Baro Pressure)
Volts or (45-55 kPa)
MAP
Baro
Volts or kPa
Volts or kPa
3-5
Volts (Depends on Altitude
and Barometric Pressure)
12.0-14.5 Volts
-10 to 30°
Bat
Volts
Spark Advance
Degrees
Knock Retard
Degrees
0°
Idle Air Control IAC
Minimum IAC Position
Idle Air Control Follower
Injector Pulse Width
Counts (Steps)
Counts (Steps)
Counts (Steps)
msec.
0-40 Counts
0-40 Counts
0 Counts
2-3 msec.
2.5-3.5
msec. (Depends on
Injector On Time Cranking
msec.
Water/Air Temperature)
1-2 GPH(3.7-7.5 L/h)
Varies
Fuel Consumption
Time From Start
GPH (L/h)
0:00:00-1092:00
Index
Page 5E-2
90-861326--1 MARCH 1999
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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