Fiat Bravo Service Manual page 177

Engine
Fuel system
Bravo-Brava ^
16v
10.
NOTE Sensor angular position may not be
adjusted in any way.
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— 1
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1. Deflector
2. Magnetic material
3. Gap
Wiring connector
The numbers in boxes indicate the corre­
sponding control unit pins
TIMING SENSOR (SFA 200)
The I.A.W.-1AF.13 system adopts a phased,
sequential injection system. In other words,
fuel is injected into each cylinder in sequence
during the intake phase.
To achieve this, the ECU uses a timing signal
together with the rpm and TDC signal to de­
termine the point of injection.
This signal is generated by a Hall sensor fitted
on the exhaust camshaft pulley.
Principle of operation
A semi-conducting layer with current flow­
ing through it is placed in a normal magnetic
field (force lines at right angles to current di­
rection). A potential difference known as a
HALL voltage is set up at its terminals.
If current intensity remains constant, the volt­
age generated depends solely on the intensi­
ty of the magnetic field; magnetic field inten­
sity need therefore only vary periodically to
set up a modulated electrical signal with fre­
quency proportional to the speed with which
the magnetic field changes.
To achieve this change, the sensor is crossed
by a metal ring (internal part of pulley) with
an opening. The moving metal part of the ring
covers the sensor and blocks the magnetic
field to produce a low output signal. The sen­
sor generates a high signal when aligned
with the opening, i.e. with magnetic field
present.
The alternation of signals is therefore depen­
dent on the succession of openings (see
chapter on "signal management").
Removing-refitting
To gain access to the timing sensor, remove
the intake side camshaft pulley (3) (refer to
engine service manual, publication no.
504.589/20).
Disconnect electrical connection of sensor.
Unscrew both screws (1) and remove timing
sensor (2) with retaining plate.
30
Publication no. 506.670