ABS electronic control unit
M50 is supplied
(at pins 17 and 18) directly by the battery via a line protected
by the ABS maxifuse, located directly on the battery A1 - connector
C.
The supply controlled by the ignition (15/54)
reaches pin 15 from the line protected by fuse
F6 of the additional
fuse box B98 A.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.
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.
This signal causes the warning light to
come on because the instrument
E30 supply is controlled by the
ignition (INT) from the line protected by fuse F4 of the additional
fuse box B98 B.
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.