Manifold Pressure Sensor; (Vacuum Sensor) - Toyota COMPUTER-CONTROLLED SYSTEM Training Manual

ELECTRONIC CONTROL SYSTEM - Manifold Pressure Sensor (Vacuum Sensor )
MANIFOLD PRESSURE SENSOR
(VACUUM SENSOR )
The manifold pressure sensor is used with D-
type EFI for sensing the intake manifold
pressure .
This is one of the most important sensors in D-
type EFI .
By means of an IC built into this sensor, the
manifold pressure sensor senses the intake
manifold pressure as a PIM signal . The Engine
ECU then determines the basic injection duration
and basic ignition advance angle on the basis of
this PIM signal .
Intake manifold pressure
OHP 9
A change in the intake manifold pressure causes
the shape of the silicon chip to change, and the
resistance value of the chip fluctuates in
accordance with the degree of deformation .
This fluctuation in the resistance value is
converted to a voltage signal by the IC built into
the sensor and is then sent to the Engine ECU
from the PIM terminal as an intake manifold
pressure signal . The VC terminal of the Engine
ECU supplies a constant 5 volts as a power
source for the IC .
(V)
4
~
rn
3
OHP 9
f
Intake manifold pressure
OPERATION AND FUNCTION
OHP 9
A silicon chip combined with a vacuum chamber
maintained at a predetermined vacuum is
incorporated into the sensor unit . One side of
the chip is exposed to intake manifold pressure
and the other side is exposed to the internal
vacuum chamber .
Engine EC U
0 20 60 100 kPa (abs)
(760, 29 .9) (610, 24 .0) (310,
1 2 .2)
(10, 0 .4) (mmHg ,
in .Hg
Intake manifold pressure
[vacuum] )
ELECTRICAL CIRCUITR Y
Manifold pressure
sensor
1
5 V
R
IC
V C
PI M
E 2
El
To intake manifol d
Silicon chip
/
OHP 10
17