Engine Electrical System

WORKING PRINCIPLE OF ELECTRONIC FUEL INJECTION
CONTROL AND ACTUATORS
※ Intake Pressure and Intake Air Temperature
Sensor
Purpose: detects manifold absolute pressure from
0.1~0.2bar and intake air temperature, provides engine
with load information.
Composition and principle: this sensor is composed
of two different sensors (i.e. manifold absolute
pressure sensor and intake temperature sensor), and is
installed above pressurizer.
Pressure-sensitive element inside intake pressure
sensor detects pressure signal on intake manifold for
injection pulse width control of EFI system. This
sensor also serves as the substitute of load signal
sensor.
Intake air temperature sensing element is a resistor
of negative temperature coefficient (NTC), which is
similar to water temperature sensor with resistance
value decreasing with the increasing of intake air
temperature. And engine ECU monitors the variation
of intake air temperature via a comparison circuit
inside.
Failure diagnosis: The electronic device next to
intake pressure sensor detects sensor circuit troubles
such as open circuit, short circuit and sensor damages,
etc. In case ECU detects any sensor output signal that
goes beyond output characteristic curve, the sensor is
diagnosed as failed by ECU. For example: when
intake pressure is higher than upper limit or lower than
lower limit, ECU detects sensor failure (in case that
intake pressure is lower than lower limit when starting,
ECU is able to recognize the starting condition), and
the engine fault indicating lamp goes on. Under this
condition the engine works in failure mode.
Installation: to be installed on pressurizer.
Circuit diagram of manifold absolute
pressure and intake air temperature sensor
Pins:
1# is grounded (connecting ECU 17#);
2# outputs temperature signal
(connecting ECU 40#);
3# connects with standard 5V power
source (connecting ECU 33#);
4# outputs pressure signal (connecting
ECU 37#).
Manif
old absolute
pressure and intake air
temperature sensor
TMAP
E-7
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