SECTION 12: BRAKE AND AIR SYSTEM
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
27
NOTE
ABS is active on service brake, transmission
retarder, Jake brake, but is inactive on
emergency/parking brake.
NOTE
The ABS system is inoperative at speeds
under 4 mph (6 Km/h). Illumination of ABS
telltale indicator at these speeds is normal.
CAUTION
Disconnect the ECU or pull the ABS fuse
before towing vehicle.
29.1
TROUBLESHOOTING AND TESTING
For troubleshooting and testing of the vehicle's
anti-lock braking system, refer to Bendix
applicable booklet annexed to this section under
reference number SD-13-4869.
29.2 ABS
COMPONENTS
The main components of the ABS system are
listed hereafter. Refer to each component for its
specific function in the system and for proper
maintenance.
29.3
BENDIX EC-60 ADVANCED
CONTROLLER
This control unit, also known as ABS module, is
located in the front electrical and service
compartment. According to the data transmitted
by the sensors (number of pulses/sec is
proportional to the speed of each wheel), the
electronic control unit determines which wheel is
accelerating or decelerating. It then establishes
a reference speed (average speed) from each
wheel data, and compares the speed of each
wheel with this reference speed to determine
which wheel is accelerating or decelerating.
As soon as wheel deceleration or wheel slip
threshold values are exceeded, the electronic
control unit signals a solenoid control valve to
limit the excessive brake pressure produced by
the driver in the appropriate brake chamber.
Maintenance
No specific maintenance is required. The ECU is
not serviceable. When found to be defective,
replace.
FIGURE 41: ABS ECU LOCATION
06617
CAUTION
In order to protect the ABS electronic control
unit from voltage surges, always disconnect
before performing any welding procedure on
vehicle.
29.4 SENSORS
The sensors are mounted on the front, drive and
tag axle (if applicable) wheel hubs. The inductive
sensors consist essentially of a permanent
magnet with a round pole pin and a coil. The
rotation of the toothed wheel alters the magnetic
flux picked up by the coil, producing an
alternating voltage, the frequency of which is
proportional to wheel speed. When wheel speed
decreases, magnetic flux decreases proportion-
ately. Consequently, the electronic control unit
will command the solenoid control valve to
decrease the pressure at the corresponding
brake chamber.
Maintenance
No specific maintenance is required for sensors,
except if the sensors have to be removed for
axle servicing. In such a case, sensors should
be lubricated with special grease (Prevost
#680460) before reinstallation. Refer to
paragraph
“Sensor Installation”
for details.
