Hummer H1 Service Manual page 142

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PEDAL AND ARM
POTENTIOMETER
MODULE
Figure 3-7: Electronic Accelerator Pedal
Components
CONNECTOR
ACCELERATOR PEDAL
Figure 3-8: Electronic Accelerator Pedal
(Location)
CONNECTOR
CLIP
Figure 3-9: Accelerator Pedal Connector Clip
5745159
BRACKET
FRONT OF
VEHICLE
Fuel, Emissions, and Exhaust
Electronic Fuel Injection Pump Operation
The electronic fuel injection pump is operated by the power-
train control module. The pump contains a fuel solenoid driver,
an optical and fuel temperature sensor, a shut off solenoid, a
stepper motor, and a fuel solenoid. Additional signal sources
that affect pump operation are: crankshaft position sensor,
boost sensor, coolant temperature sensor, intake air tempera-
ture sensor, and electronic accelerator pedal.
At initial engine start, the fuel/lift pump continuously supplies
fuel to the injection pump.
A change in accelerator pedal position to part throttle, causes
an equivalent change in pedal potentiometer voltage output.
The PCM then signals the solenoid driver to increase fuel flow.
Flow rates are further refined based on various signals from en-
gine sensors.
The boost/baro sensor monitors changes in intake manifold
pressure. Pressure changes are converted into a voltage signal
transmitted to the PCM. High voltage readings indicate high
manifold pressures and low voltage indicates low pressure.
The intake air temperature sensor monitors incoming air tem-
perature. Cold air generates high sensor resistance readings
while warm air generates lower readings. The resistance sig-
nals are transmitted to the PCM which richens or leans the fuel
mixture as needed.
Barometric pressure is monitored by the baro sensor. The sen-
sor signal is used by the PCM to adjust injection pump timing
and fuel mixture for different altitudes.
The stepper motor advances/retards injection timing on com-
mand by the PCM. Signals from the optical, air temperature,
crankshaft position, coolant temperature, and fuel temperature
sensors, are all utilized by the PCM to optimize settings.
Fuel injector cycles are monitored by the PCM (which controls
injection). The fuel solenoid driver returns a pulse width signal
to the PCM every time it seats the fuel solenoid. This signal in-
dicates injection has occurred at one of the injectors, and the
length of the injection cycle.
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