The ABS electronic control unit
M50
is supplied (at pin 2 and 6) directly by the battery via a line
protected by ABS maxifuse
B7
.
Ignition-operated power supply (INT/A) reaches
pin 15 of the line protected by shunt fuse
B31
. The control
unit is earthed via pins 19 and 16 (
C12
).
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.
The brake pedal switch
I30
sends
an enablement signal to pin 32 of control unit
M50
. The
ABS is deactivated entirely unless the brake pedal is pressed.
Brake pedal signal
I30 is also used to
control the BRAKE lights (
See
E6021
COMPRESSOR ENGAGEMENT
)
and ENGINE CONTROL UNIT M10 (
See
E5030
PETROL ENGINE ELECTRONIC
MANAGEMENT
See
E5050
DIESEL ENGINES ELECTRONIC MANAGEMENT
).
A second contact on brake pedal
I30 (pins
3-4) sends a signal to control unit M10, which manages the CRUISE
CONTROL system
See
E5060
CRUISE CONTROL
,
when the pedal is pressed.
Pin 22 of
M50
produces a speedometer
signal (average speed of all four wheels) which is directed to instrument
panel
E50
- pin 2 of connector B (
See E4010 INSTRUMENT PANEL
).
The ABS includes a self-diagnostic system:
when the control unit detects problems with the ABS, it sends a
signal from pin 20 of instrument
E50
- pin 18 of connector
C - which turns on the ABS fault warning light.
The red warning light is of the type known
as 'smart' warning lights because an inner control circuit causes
the warning light to light up even if the connection is broken or
if the circuit connecting warning light and control unit is short-circuited
to earth.
If the problems lie in the EBD function,
the control unti also sends a signal from pin 21 to instrument
E50
- pin 19 of connector C - to the low brake fluid and handbrake warning light.
Both signals sent to the instrument are
earth, and they turn on the warning lights since instrument
E50
is ignition-activated (INT/A) from a line protected by fuse
F1
of junction unit
B1
.
The self-test 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.