5.0/5.7/6.0L/8.1L General Information 1 - 5
MEFI 4 - PCM
XXXXXXXXXXXXXXX DEFAULTXXXXXXXXXXX
XXXXXXXXXXXXXXX DEFAULTXXXXXXXXXXX
------50 -4.2V OUT OF RANGE SENSOR
------150 -1.7V ACTUAL COOLANT TEMPERATURE
HIGH TEMP - 0 VOLTS
LOW TEMP - 5 VOLTS
6-5-93
MS 13552
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Figure 1-3 - Example of Shifted Sensor Operation
Aftermarket (Add-On) Electrical And Vacuum
Equipment
Aftermarket, add-on electrical and vacuum equipment is
defi ned as any equipment installed on a vehicle after
leaving the factory that connects to the vehicles electrical
or vacuum systems.
Notice: Do not attach add-on vacuum operated
equipment to this engine. The use of add-on vacuum
equipment may result in damage to engine components
or systems.
Notice: Connect any add-on electrically operated
equipment to the vehicle’s electrical system at the battery
(power and ground) in order to prevent damage to the
vehicle.
Add-on electrical equipment, even when installed to
these strict guidelines, may still cause the powertrain
system to malfunction. This may also include equipment
not connected to the vehicle’s electrical system such as
portable telephones and radios. Therefore, the fi rst step
in diagnosing any powertrain problem, is to eliminate all
aftermarket electrical equipment from the vehicle. After
this is done, if the problem still exists, diagnose the
problem in the normal manner.
Use of Circuit Testing Tools
Do not use a test lamp in order to diagnose the engine
electrical systems unless specifi cally instructed by the
diagnostic procedures. Use the J 35616-A connector
test adapter kit whenever diagnostic procedures call for
probing any connectors.
Tools Needed To Service The System
Refer to Special Tools in this section for engine control
tools for servicing the system.
Clearing Diagnostic Trouble Codes (Scan)
1. Install scan tool.
2. Start engine.
3. Select “clear DTC’s” function.
4. Clear DTC’s.
5. Turn ignition “OFF” for at least 20 seconds.
6. Turn ignition “ON” and read DTC’s. If DTC’s are still
present, check “Notice” below and repeat procedure
following from step 2.
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.
Non-Scan Diagnosis Of Driveability
Concerns (No DTC’s Set)
If a driveability concern still exists after following the OBD
system check and reviewing the Symptoms section, an
out of range sensor may be suspected. Because of the
unique design of the MEFI system, the ECM will replace
sensed values with calibrated default values in the case of
a sensor or circuit malfunction. By allowing this to occur,
limited engine performance is restored until the boat
is repaired. A basic understanding of sensor operation
is necessary to be able to diagnose an out of range
sensor.
If the sensor is out of range, but still within the operating
“window” of the ECM, the problem will go undetected by the
ECM and may result in a driveability concern.
A good example of this would be if the coolant sensor was
reading incorrectly and indicating to the ECM that coolant
temperature was at 50°F, but actual coolant temperature
was at 150°F (Figure 1-3). This would cause the ECM to
deliver more fuel than what was actually needed by the
engine. This resulted in an overly rich condition, causing
rough running. This condition would not have caused
a DTC to set, as the ECM interprets this as within the
operating “window.”
To identify a sensor that is out of range, you may unplug
the sensor electrical connector while the engine is running.
After about 2 minutes, the DTC for that sensor will set,
illuminate the MIL, and replace the sensed value with
a calibrated default value. If at that point, a noticeable
performance increase is observed, the non-scan DTC
table for that particular sensor may be followed to correct
the problem.
NOTICE: Be sure to clear each DTC after disconnecting
and reconnecting each sensor. Failure to do so may result
in a misdiagnosis of the driveability concern.
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