1 - 4 General Information
5.0/5.7/6.0/8.1L
MEFI 4 - PCM
XXXXXXXXXXXXXXX DEFAULTXXXXXXXXXXX
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0 VOLTS
5 VOLTS
6-5-93
MS 13553
V
O
L
T
A
G
E
TYPICAL SENSOR RANGE
“WINDOW”
4.6V
0.7V
Figure 1-2 - Example of Sensor Normal Operation
Clearing Diagnostic Trouble Codes (Non-
Scan)
1. Install Diagnostic Trouble Code (DTC) tool.
2. Ignition “ON,” engine “OFF.”
3. Switch DTC tool to “service mode” or “ON.”
4. Move the throttle from 0% (idle) to 100% (WOT) and
back to 0%.
5. Switch DTC tool to “normal mode” or “OFF.” (If this
step is not performed, the engine may not start and
run).
6. Turn ignition “OFF” for at least 20 seconds.
7. Ignition “ON,” engine “OFF.”
8. Switch DTC tool to “service mode” or “ON” and verify
DTC 12 only. Remove DTC tool.
9. If original DTC(s) are still present, check “Notice” below
and repeat the DTC clearing procedure.
10. If new DTC(s) are displayed, perform the OBD system
check.
NOTICE:
When clearing DTC’s with or without the use of a
scan tool, the ignition must be cycled to the “OFF” position
or the DTC’s will not clear.
Scan Tool Use With Intermittents
The scan tool provides the ability to perform a “wiggle test”
on wiring harnesses or components with the engine not
running, while observing the scan tool display.
The scan tool can be plugged in and observed while
driving the boat under the condition when the MIL turns
“ON” momentarily, or when the engine driveability is
momentarily poor. If the problem seems to be related to
certain parameters that can be checked on the scan tool,
they should be checked while driving the boat. If there
does not seem to be any correlation between the problem
and any specifi c circuit, the scan tool can be checked on
each position, watching for a period of time to see if there
is any change in the readings that indicates intermittent
operation.
The scan tool is also an easy way to compare the operating
parameters of a poorly operating engine with those of a
known good one. For example, a sensor may shift in value
but not set a DTC.
The scan tool has the ability to save time in diagnosis
and prevent the replacement of good parts. The key to
using the scan tool successfully for diagnosis lies in the
technicians ability to understand the system they are trying
to diagnose, as well as an understanding of the scan tool
operation and limitations. The technician should read the
tool manufacturer’s operating manual to become familiar
with the tool’s operation.
How Diagnostic Trouble Codes (DTC) Are Set
The ECM is programmed to receive calibrated voltage
signals from the sensors. The voltage signal from the
sensor may range from as low as 0.1 volt to as high
as 4.9 volts. The sensor voltage signal is calibrated for
engine application. This would be the sensor’s operating
parameter or “window.” The ECM and sensors will be
discussed further in the ECM and Sensor section.
If a sensor is within its operating or acceptable parameters
(Figure 1-2), the ECM does not detect a problem. When a
sensor voltage signal falls out of this “window,” the ECM
no longer receives a signal voltage within the operating
“window.” When the ECM does not receive the “window”
voltage for a calibratible length of time, a DTC will be
stored. The MIL will be illuminated and a known default
value will replace the sensor value to restore engine
performance.
Summary of Contents for 5.0L
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