PREVOST X3-45 COMMUTER Maintenance Manual Download

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SECTION 12: BRAKE AND AIR SYSTEM

DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)

CAUTION

Even with ESC-equipped vehicles, the driver
remains responsible for ensuring vehicle
stability during operation.

MAINTENANCE

ABS & ELECTRONIC STABILITY
CONTROL SYSTEMS

Every 12 months,

Check the proper functioning of ABS and ESC
systems. To do so, perform the “Component
Test” using Bendix ACom Diagnostics
software.

Bendix ACom Diagnostics software is
available for download at www.bendix.com.

30.1 COMPONENTS

30.1.1 The EC-60

controller’s ABS function

utilizes the following components:



Six (6) Bendix

WS-24

wheel speed

sensors. Each sensor is installed with a
Bendix Sensor Clamping Sleeve;



Five (5) Bendix

Pressure Modulator

Valves (M-40QR);



Dash-mounted vehicle ABS Indicator

Lamp;



Service brake relay valve;



Dash-mounted

trailer ABS Indicator Lamp.

30.1.2 The EC-60

controller’s ATC function

utilizes the following components:



Drive axle traction control valve;



Dash-mounted ESC/TCS status/indicator

lamp (also serves as the ESC sta-
tus/indicator lamp);



Dash-mounted TCS Mud/Snow switch;



J1939 serial communication to engine

control module.

30.1.3 The

EC-60

controller’s ESC/RSP

function utilizes the following components:



Front Axle Traction Control Valve integral

to the service brake relay valve;



Dash-mounted ESC/TCS status/indicator

lamp (also serves as the ATC sta-
tus/indicator lamp);



Bendix SAS-70 Steering Angle Sensor

(mounted to the steering column);



Bendix YAS-70 Yaw Rate/Lateral Acceler-

ation Sensor (mounted to a cross member
forward of the drive axle);



Brake Demand Sensors (installed in the

primary and secondary delivery circuits);



An additional Modulator Valve (Bendix

M-40QR

Pressure Modulator Valve) that

controls pressure applied to the trailer
brakes during system intervention.

30.2

BENDIX M-40QR PRESSURE
MODULATOR VALVE

This Bendix

M-40QR (quick release) Pressure

Modulator Valve (PMV) is operated by the EC-
60 controller to modify driver applied air
pressure to the service brakes during ABS, ATC,
RSP or YC activation. The PMV is an electro
pneumatic control valve and is the last valve that
air passes through on its way to the brake
chamber. The modulator hold and release
solenoids are activated to “modulate” or “control”
the brake pressure during an antilock braking
event. The hold solenoid is normally open and
the release solenoid is normally closed, such
that the PMV nominally allows air to flow
through. This design allows for air delivery to
brake chambers in the event of electrical trouble.
This is an

"On/Off"

type valve, i.e., during an

antilock activity, the valve exhausts air from the
brake chamber when in a ABS event, the
electronic unit senses that the corresponding
wheel speed is decreasing in relation to the
other wheels.
The Advanced EC-60 controller also utilizes an
additional PMV for control of the trailer service
brakes during stability interventions.

6s/5m Configuration

Prevost vehicles utilize a 6 sensors/5 pressure
modulator valves configuration, with the tag axle
having two sensors, but only one Pressure
Modulator Valve. In this case, the PMV controls
both wheels on the tag axle. The tag axle
wheels would receive equal brake pressure,
based on the wheel that is currently experienc-
ing the most wheel slip.