Intake manifold air temperature sensor-pcm input. Manifold absolute pressure (map) sensor-pcm input
DESCRIPTION The 2-wire Intake Manifold Air Temperature (IAT)
sensor is installed in the intake manifold with the
sensor element extending into the air stream.
The IAT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as intake manifold
temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resistance
(voltage) in the sensor increases. OPERATION The IAT sensor provides an input voltage to the
Powertrain Control Module (PCM) indicating the
density of the air entering the intake manifold based upon intake manifold
temperature. At key-on, a
5-volt power circuit is supplied to the sensor from
the PCM. The sensor is grounded at the PCM
through a low-noise, sensor-return circuit.
The PCM uses this input to calculate the following: The resistance values of the IAT sensor is the same
as for the Engine Coolant Temperature (ECT) sensor. DESCRIPTION The Manifold Absolute Pressure (MAP) sensor is
attached to the side of the engine throttle body with
2 screws. The sensor is connected to the throttle body
with a rubber L-shaped fitting. OPERATION The MAP sensor is used as an input to the Powertrain
Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the combustion
chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at maximum.
A 5 volt reference is supplied from the PCM and
returns a voltage signal to the PCM that reflects
manifold pressure. The zero pressure reading is 0.5V
and full scale is 4.5V. For a pressure swing of 0-15
psi, the voltage changes 4.0V. To operate the sensor,
it is supplied a regulated 4.8 to 5.1 volts. Ground is
provided through the low-noise, sensor return circuit
at the PCM.
The MAP sensor input is the number one contributor
to fuel injector pulse width. The most important
function of the MAP sensor is to determine barometric
pressure. The PCM needs to know if the vehicle is
at sea level or at a higher altitude, because the air
density changes with altitude. It will also help to correct
for varying barometric pressure. Barometric
pressure and altitude have a direct inverse correlation;
as altitude goes up, barometric goes down. At
key-on, the PCM powers up and looks at MAP voltage,
and based upon the voltage it sees, it knows the
current barometric pressure (relative to altitude).
Once the engine starts, the PCM looks at the voltage
again, continuously every 12 milliseconds, and compares
the current voltage to what it was at key-on.
The difference between current voltage and what it
was at key-on, is manifold vacuum. During key-on (engine not running) the sensor
reads (updates) barometric pressure. A normal range
can be obtained by monitoring a known good sensor.
As the altitude increases, the air becomes thinner
(less oxygen). If a vehicle is started and driven to a
very different altitude than where it was at key-on,
the barometric pressure needs to be updated. Any
time the PCM sees Wide Open Throttle (WOT), based
upon Throttle Position Sensor (TPS) angle and RPM,
it will update barometric pressure in the MAP memory
cell. With periodic updates, the PCM can make
its calculations more effectively.
The PCM uses the MAP sensor input to aid in calculating
the following: The MAP sensor signal is provided from a single
piezoresistive element located in the center of a diaphragm.
The element and diaphragm are both made
of silicone. As manifold pressure changes, the diaphragm
moves causing the element to deflect, which
stresses the silicone. When silicone is exposed to
stress, its resistance changes. As manifold vacuum
increases, the MAP sensor input voltage decreases
proportionally. The sensor also contains electronics
that condition the signal and provide temperature
compensation.
The PCM recognizes a decrease in manifold pressure
by monitoring a decrease in voltage from the
reading stored in the barometric pressure memory
cell. The MAP sensor is a linear sensor; meaning as
pressure changes, voltage changes proportionately.
The range of voltage output from the sensor is usually
between 4.6 volts at sea level to as low as 0.3
volts at 26 in. of Hg. Barometric pressure is the pressure
exerted by the atmosphere upon an object. At
sea level on a standard day, no storm, barometric
pressure is approximately 29.92 in Hg. For every 100
feet of altitude, barometric pressure drops.10 in. Hg.
If a storm goes through it can change barometric
pressure from what should be present for that altitude.
You should know what the average pressure
and corresponding barometric pressure is for your
area.Intake manifold air temperature sensor-pcm input
Manifold absolute pressure (map) sensor-pcm input
Dodge Durango (DN) 1998-2003 Service Manual
- Lubrication and Maintenance
- Suspension
- Differential and Driveline
- Brakes
- Cooling System
- Battery
- Starting Systems
- Charging System
- Ignition System
- Instrument Panel Systems
- Audio Systems
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- Speed Control System
- Turn Signal and Hazard Warning Systems
- Wiper and Washer Systems
- Lamps
- Passive Restraint Systems
- Electrically Heated Systems
- Power Distribution System
- Power Lock Systems
- Vehicle Theft/Security Systems
- Power Seat System
- Power Window Systems
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- Overhead Console Systems
- Engine
- Exhaust System
- Frame and Bumpers
- Fuel System
- Steering
- Transmission and Transfer Case
- Tires and Wheels
- Body
- Heating and Air Conditioning
- Emission Control Systems
- Introduction