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28
Group
Ignition systems
Design
and function - System descriptions
•
R
A
The above figures illustrate
which
occurs in
the
course of commun ication between
tracing
.
Construction and connections
The diagnostic unit
consists of
con nected
to ground when the switch is
resistor and switch. Socket No.6 is connected to
Grounding of terminal
a
single component in
mina!
20.
The
signal transistor
The battery
supplies
power to
that the
memory is
not
(Picture
Power is supplied
to
control unit
Voltage is present
at
terminal
unit.
Signal from diagnostic: unit
The
control
unit must be supplied with
This
information is
supplied
(The
direction
of
the arrows
The switch is
closed
by depressing the
from the
battery,
across ignition switch terminal
8.
This
causes
the LED to
unit determines whether the self-diagnostic function
whether
the
voltage
at
66
the
construction of the diagnostic
AI
(Picture
an LED
resistor
closed.
is
monitored by a
signal
1
the figures) which
alternately
is controlled
by the diagnostic
control
unit terminal
erased
when the ignit
B)
term
inal 6 across ign
1 on the
control
unit when the
Cl
(Picture
some
across the normally-open switch
in
this picture
shows
pushbutton,
light,
while the
voltage
terminal
1
has fallen
to
I
A
D
unit
(1),
the
unit and
the
(R)
and a normally-open switch
A
connection
point for the
terminal
1
on
the ignition system
transistor
(actually a transistor network, although symbolized
(4)
opens and
closes
circuit (5)
5
and to the diagnostic
ion is
switched
off.
ition switch
termi
coding cable is inserted in
(pushbutton
that the
signal
flows from the
grounding terminalS
15,
through the diagnostic unit and finally to ground across terminal
normally present at control unit terminal 1 falls to 0
or
functional
test program has been selected by detecting
zero
once
or
twice.
its
connections,
and
the
ign
ition
system
control
(push
button
coding
cable
(3)
is provided between
control
unit.
the ground connection across control
in the
control
unit.
circuit
in the control
nal 15 when the key is turned to position
socket
No.
A).
diagnostic
unit to the
on
the diagnostic
unit.
sequence of events
unit
during fault
(2)
A).
Terminal
8
is
the
by
unit
ter·
unit.
This ensures
II.
6
on
the diagnostic
to
be activated.
control unit.)
Current then flows
V.
The control
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