5.0/5.7/6.0L/8.1L ECM and Sensors 2 - 5
MEFI 4 - PCM
ECM Inputs and Sensor Descriptions
Figure 2-5 lists the data sensors, switches, and other inputs
used by the ECM to control its various systems. Although
we will not cover them all in great detail, there will be a
brief description of each.
Input Components
The ECM monitors the input components for circuit
continuity and out-of-range values. This includes
performance checking. Performance checking refers to
indicating a fault when the signal from a sensor does not
seem reasonable, such as a throttle position (TP) sensor
that indicates high throttle position at low engine loads or
MAP voltage. The input components may include, but are
not limited to, the following sensors:
• Intake air temperature (IAT) sensor (5.0/5.7L only)
• Crankshaft position (CKP) sensor
• Camshaft position (CMP) sensor
• Knock sensor(s) (KS)
• Throttle position (TP) sensor
• Engine coolant temperature (ECT) sensor
• Manifold absolute pressure (MAP) sensor
Output Components
Diagnose the output components for the proper response
to ECM commands. Components where functional
monitoring is not feasible, will be monitored for circuit
continuity and out-of-range values, if applicable.
Output components to be monitored include, but are not
limited to, the following circuits:
• The malfunction indicator lamp (MIL) control
• The check gauges lamp control
• The general warning 2 (low oil pressure) lamp
control
Speed Density System
The Marine Electronic Fuel Injection (MEFI) system is a
speed and air density system. The system is based on
“speed density” fuel management.
Sensors provide the ECM with the basic information for
the fuel management portion of its operation. Signals
to the ECM establish the engine speed and air density
factors.
Speed
The engine speed signal comes from the CKP sensor to
the ECM. The ECM uses this information to determine the
“speed” or RPM factor for fuel and spark management.
Density
One particular sensor contributes to the density factor,
the Manifold Absolute Pressure (MAP) sensor. The MAP
sensor is a 3-wire sensor that monitors the changes in
intake manifold pressure which results from changes in
engine loads. These pressure changes are supplied to the
ECM in the form of electrical signals.
As intake manifold pressure increases, the vacuum
decreases. The air density in the intake manifold also
increases, and additional fuel is needed.
The MAP sensor sends this pressure information to the
ECM, and the ECM increases the amount of fuel injected,
by increasing the injector pulse width. As manifold pressure
decreases, the vacuum increases, and the amount of
fuel is decreased.
These two inputs, MAP and RPM, are the major
determinants of the air/fuel mixture delivered by the fuel
injection system. The remaining sensors and switches
provide electrical inputs to the ECM, which are used for
modifi cation of the air/fuel mixture, as well as for other
ECM control functions, such as idle control.
To Next Page
Loading...
Need help?
General
