Chrysler 1998 Voyager Service Manual page 1413

NS/GS
DESCRIPTION AND OPERATION (Continued)
BOOST PRESSURE SENSOR
The Boost Pressure Sensor is mounted to the top of
the intake manifold. (Fig. 2) It is a sensor that mea-
sures both manifold vacuum and turbo boost, and it
also contains an integrated intake air temperature
sensor. The Boost Pressure Sensor takes the place of
the Mass Air Flow (MAF). In the Intake Air Temper-
ature Sensor component, there is a ceramic element
that changes its resistance based on temperature.
The ceramic element is part of an electronic circuit
connected to the PCM, and has a voltage applied to
it. The ceramic element is exposed to the air inside
the intake. This air has a cooling effect on the
ceramic element, and its resistance changes. This
causes the voltage flowing through the intake air
temperature circuit to vary. The voltage signal pro-
duced by the Intake Air Temperature Sensor changes
inversely to the temperature, and is measured by the
PCM. As a general rule, when the temperature of the
air in the intake is high, the voltage signal produced
by the Intake Air Temperature Sensor is low. The
component of the Boost Pressure Sensor that mea-
sures manifold vacuum and turbo boost produces a
voltage signal that is proportional to the pressure in
the inake manifold. When the intake manifold pres-
sure is low, the voltage is low, and when the pressure
is high, the voltage is high. The PCM uses the volt-
age signals from the Boost Pressure Sensor, and the
Intake Air Temperature Sensor to determine the
amount of air flowing through the intake manifold.
Fig. 2 Boost Pressure Sensor Location
VEHICLE THEFT ALARM
The PCM can learn if the vehicle has a Vehicle
Theft Alarm (VTA) system. Once it detects the vehi-
cle having VTA, the controller can ONLY BE
USED ON VEHICLES WITH VTA.
FUEL SYSTEM—2.5L DIESEL ENGINE/2.0L GAS ENGINE
If the PCM is put it on a vehicle without VTA the
Glow Plug Lamp will start to blink and the vehicle
will not start.
The PCM cannot be flashed to remove the VTA.
BATTERY VOLTAGE—PCM INPUT
The battery voltage input provides power to the
PCM. It also informs the PCM what voltage level is
being supplied by the generator once the vehicle is
running.
The battery input also provides the voltage that is
needed to keep the PCM memory alive. The memory
stores Diagnostic Trouble Code (DTC) messages.
Trouble codes will still be stored even if the battary
voltage is lost.
SENSOR RETURN—PCM INPUT (ANALOG
GROUND)
Sensor Return provides a low noise Analog ground
reference for all system sensors.
SIGNAL GROUND—PCM INPUT
Signal ground provides a low noise ground to the
data link connector.
IGNITION CIRCUIT SENSE—PCM INPUT
The ignition circuit sense input signals the PCM
that the ignition (key) switch has been turned to the
ON position. This signal initiates the glow plug con-
trol routine to begin the "pre–heat" cycle.
START SIGNAL—PCM INPUT
This input tells the PCM that the engine starter is
being operated. This in turn will start the glow plug
"post–heat" cycle.
POWER GROUND
Provides a common ground for power devices (sole-
noid and relay devices).
NEEDLE MOVEMENT OR INSTRUMENTED FIRST
INJECTOR—PCM INPUT
This input from the PCM supplies a constant 30
mA electrical current source for the first injector sen-
sor. It will vary the voltage to this sensor when it
senses a mechanical movement within the injector
needle (pintle) of the number–1 cylinder fuel injector.
When this voltage has been determined by the PCM,
it will then control an output to the fuel timing sole-
noid (the fuel timing solenoid is located on the fuel
injection pump). Also refer to Fuel Injection Pump for
additional information.
The first injector sensor is a magnetic (inductive)
type.
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