ABS electronic control unit
M50
is supplied (at pins 17
and 18) directly by the battery via a line protected by the ABS
maxifuse of
B6
up to 2/99 or by ABS maxifuse located directly
on the battery
A1
- connector C from 2/99.
The supply controlled by the ignition (15/54)
reaches pin 15 from the line protected by shunt fuse
B30
up
to 3/98) or by
B31
from 3/98 to 2/99 or from fuse
F6
from
supplementary fuse box
B98A
from 2/99.
The control unit is earthed via pins 19
and 16.
The four sensors
K70
,
K71
,
K75
,
K76
send wheel speed signals to pins 6-7, 4-5, 8-9 and 1-2
of
M50
respectively.
Brake pedal switch
I30
sends an enablement
signal to pin 14 of control unit
M50
: the ABS cannot intervene
unless the brake pedal is pressed.
If the control unit
M50
detects problems
relating to the ABS function, it sends the instrument panel
E50
a
signal, from pin 4, which lights up the "ABS failure" warning
light; if the problems concern the EBD function, the handbrake warning
light is lit up from pin 21.
Pin 22 of
M50
produces a speedometer
signal (average speed of all four wheels) which is sent to the instrument
panel
E10
. (
See E4021 SPEEDOMETER
).
The ABS includes an autodiagnostic system:
when the control unit detects problems relating to the ABS function
it sends a signal from pin 20 to the check instrument
E30
which
contains the "ABS failure" warning light. If the problems involve
the EBD function, the control unit also sends a signal from pin
21 to instrument
E30
to the "insufficient brake fluid
level" and "handbrake applied" warning light.
These are earth signals and cause the warning
lights to come on because the supply for instrument
E30
is
controlled by the ignition (INT) from the line protected by the
controls light fuse
B11
up to 2/99 or from fuse
F4
of
supplementary fuse box
B98B
from 2/99.
The autodiagnostic data can be read by connecting
to connector
R10
: it receives signals from pin 11 of the
control unit
M50
via the special diagnostic line.