PleasureCraft Engine Group 5.0L, Руководство по диагностике

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2 - 8 ECM and Sensors 5.0/5.7/6.0/8.1L
MEFI 4 - PCM
Intake Air Temperature (IAT) Sensor (5.0/5.7L)
The Intake Air Temperature (IAT) sensor is a thermistor
which changes value based on the temperature of air
entering the engine (Figure 2-12). Low temperature
produces a high resistance (100,000 ohms at -40°C/-40°F)
while high temperature causes low resistance (70 ohms
at 130°C/266°F).
The ECM supplies a 5 volt signal to the sensor through a
resistor in the ECM and measures the voltage. The voltage
will be high when the incoming air is cold, and low when
the incoming air is hot. By measuring the voltage, the
ECM calculates the incoming air temperature. The IAT
sensor signal is used to determine spark timing based on
incoming air density.
The scan tool displays temperature of the air entering the
engine, which should read close to ambient air temperature
when engine is cold, and rise as engine compartment
temperature increases. If the engine has not been run for
several hours (overnight), the IAT sensor and ECT sensor
temperatures should read close to each other. A failure in
the IAT sensor circuit should set DTC 23 or DTC 25.
Ignition Control (IC) Reference
The Ignition Control (IC) reference (RPM signal) is supplied
to the ECM by way of the crankshaft position sensor. This
pulse counter type input creates the timing signal for the
pulsing of the fuel injectors, as well as the IC functions.
This signal is used for a number of control and testing
functions within the ECM.
Throttle Position (TP) Sensor
The Throttle Position (TP) sensor is a potentiometer
connected to the throttle shaft on the throttle body.
By monitoring the voltage on the signal line, the ECM
calculates throttle position. As the throttle valve angle is
changed (accelerator pedal moved), the TP sensor signal
also changes. At a closed throttle position, the output of the
TP sensor is low. As the throttle valve opens, the output
increases so that at Wide Open Throttle (WOT), the output
voltage should be above 4 volts.
The ECM calculates fuel delivery based on throttle valve
angle (driver demand). A broken or loose TP sensor
may cause intermittent bursts of fuel from an injector
and unstable idle because the ECM thinks the throttle is
moving. A hard failure in the TP sensor circuit should set
either a DTC 21 or DTC 22. Once a DTC is set, the ECM
will use a calibratible default value for throttle position and
some engine performance will return.
1 THROTTLE POSITION (TP) SENSOR
2 TP SENSOR ATTACHING SCREW
RS 22191
1
2
Figure 2-10 - Throttle Position (TP) Sensor (Typical)
Figure 2-11 - Throttle Position (TP) Sensor (Typical)
RS 22192
1 THROTTLE POSITION (TP) SENSOR
2 THROTTLE VALVE
2
1
C
B
A
CONTROL
MODULE
Figure 2-12 - Manifold Absolute Pressure (MAP) Sensor/
Intake Air Temperature (IAT) Sensor
(Used On 5.0/5.7L Engines)