6
ECU Configuration Test
Within two seconds of the application of ignition power, the
ECU will perform a test to detect system configuration with
regards to the number of wheel speed sensors and PMVs.
This can be audibly detected by a rapid cycling of the PMVs.
(Note: The ECU will not perform the configuration test when
wheel speed sensors show that the vehicle is in motion.)
Pressure Modulator Valve Chuff Test
After the performance of the configuration test, the EC-60
™
controller will perform a Bendix-patented PMV Chuff Test.
The Chuff Test is an electrical and pneumatic PMV test
that can assist maintenance personnel in verifying proper
PMV wiring and installation.
With brake pressure applied, a properly installed PMV will
perform one sharp audible exhaust of air by activating the
hold solenoid twice and the release solenoid once. If the
PMV is wired incorrectly, it will produce two exhausts of air
or none at all.
The EC-60
™
controller will perform a PMV chuff test on all
installed modulators in the following order:
• Steer Axle Right PMV
• Steer Axle Left PMV
• Drive Axle Right PMV
• Drive Axle Left PMV
• Additional Axle Right PMV
• Additional Axle Left PMV
The pattern will then repeat itself.
The ECU will not perform the PMV Chuff Test when wheel
speed sensors show that the vehicle is in motion.
ABS OPERATION
Bendix ABS uses wheel speed sensors, ABS modulator
valves, and an ECU to control either four or six wheels of a
vehicle. By monitoring individual wheel turning motion during
braking, and adjusting or pulsing the brake pressure at each
wheel, the EC-60
™
controller is able to optimize slip between
the tire and the road surface. When excessive wheel slip,
or wheel lock-up, is detected, the EC-60
™
controller will
activate the Pressure Modulator Valves to simulate a driver
pumping the brakes. However, the EC-60
™
controller is
able to pump the brakes on individual wheels (or pairs of
wheels), independently, and with greater speed and
accuracy than a driver.
Steer Axle Control
Although both wheels of the steer axle have their own wheel
speed sensor and pressure modulator valve, the EC-60
™
controller blends the applied braking force between the two
steering axle brakes. This Bendix patented brake application
control, called Modified Individual Regulation (MIR), is
designed to help reduce steering wheel pull during an ABS
event on road surfaces with poor traction (or areas of poor
traction, e.g. asphalt road surfaces with patches of ice).
Single Drive Axle Control (4x2 Vehicle)
For vehicles with a single rear drive axle (4x2), the brakes
are operated independently by the EC-60
™
controller, based
on the individual wheel behavior.
Dual Drive Axle Control (4S/4M Configuration)
For vehicles with dual drive axles (6x4) using a 4S/4M
configuration, one ABS modulator controls both right-side
rear wheels and the other modulator controls both left-side
rear wheels. Both wheels on each side receive equal brake
pressure during an ABS stop. The rear wheel speed sensors
must be installed on the axle with the lightest load.
Dual Rear Axle Control (6S/6M Configuration)
For vehicles with dual rear axles (6x4, 6x2) using a 6S/6M
configuration, the rear wheels are controlled independently.
Therefore, brake application pressure at each wheel is
adjusted according to the individual wheel behavior on the
road surface.
6x2 Vehicles with 6S/5M Configuration
6x2 vehicles can utilize a 6S/5M configuration, with the
additional axle (a non-driven rear axle) having two sensors,
but only one Pressure Modulator Valve. In this case, the
PMV controls both wheels on the additional axle. The
additional axle wheels would receive equal brake pressure,
based on the wheel that is currently experiencing the most
wheel slip.
FIGURE 8 - VEHICLE ORIENTATION (TYPICAL)
Driver
Right Steer
Left Steer
Right
Additional
Left
Additional
Right Drive
Left Drive
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