Bendix Commercial Vehicle Systems EC-60 ATC STD/PREM CONTROLLERS - Manual (Page 9)

9
AUTOMATIC TIRE SIZE CALIBRATION
The ECU requires a precise rolling circumference ratio
between steer axle and drive axle tires in order for ABS
and ATC to perform in an optimal manner. For this reason,
a learning process continuously takes place in which the
precise ratio is calculated. This calculated value is stored in
the ECU memory provided the following conditions are met:
1. Rolling-circumference ratio is within the permissible
range.
2. Vehicle speed is greater than approximately 12 MPH.
3. No acceleration or deceleration is taking place.
4. There are no active speed sensor diagnostic trouble
codes.
The ECU is provided with a ratio value of 1.00 as a default
setting. If the automatic tire size alignment calculates a
different value, this is used to overwrite the original figure
in the memory. This process adapts the ABS and ATC
function to the vehicle.
Acceptable Tire Sizes
The speed calculation for an exciter ring with 100 teeth is
based on a default tire size of 510 revolutions per mile.
This figure is based on the actual rolling circumference of
the tires, which varies with tire size, tire wear, tire pressure,
vehicle loading, etc.
The ABS response sensitivity is reduced when the actual
rolling circumference is excessive on all wheels. For a 100
tooth exciter ring, the minimum number of tire revolutions
per mile is 426, and the maximum is 567. The ECU will
set diagnostic trouble codes if the number of revolutions
are out of this range.
In addition, the size of the steer axle tires compared to
the drive axle tires also has to be within the ABS system
design. To avoid diagnostic trouble codes, the ratio of the
effective rolling circumference of the steer axle, divided by
the effective rolling circumference of the drive axle, must
be between 0.85 to 1.15.
ABS PARTIAL SHUTDOWN
Depending which component the trouble code is detected
on, the ABS and ATC functions may be fully or partially
disabled. Even with the ABS indicator lamp on, the EC-60 ™
controller may still provide ABS function on wheels that are
not affected. The EC-60 ™ controller should be serviced as
soon as possible.
Steer Axle ABS Modulator Diagnostic Trouble
Code
ABS on the affected wheel is disabled. ABS and ATC on
all other wheels remains active.
Drive Axle/Additional Axle ABS Modulator
Diagnostic Trouble Code
ATC is disabled. ABS on the affected wheel is disabled.
ABS on all other wheels remains active.
Steer Axle Wheel Speed Sensor Diagnostic
Trouble Code
The wheel with the diagnostic trouble code is still controlled
by using input from the remaining wheel speed sensor on
the front axle. ABS remains active on the rear wheels.
ATC is disabled.
Drive Axle/Additional Axle Wheel Speed Sensor
Diagnostic Trouble Code
ATC is disabled. In a four sensor system, ABS on the
affected wheel is disabled, but ABS on all other wheels
remains active.
In a six sensor system, ABS remains active by using input
from the remaining rear wheel speed sensor on the same
side.
ATC Modulator Diagnostic Trouble Code
ATC is disabled. ABS remains active.
J1939 Communication Diagnostic Trouble Code
ATC is disabled. ABS remains active.
ECU Diagnostic Trouble Code
ABS and ATC are disabled. The system reverts to normal
braking.
Voltage Diagnostic Trouble Code
While voltage is out of range, ABS and ATC are disabled.
The system reverts to normal braking. When the correct
voltage level is restored, full ABS and ATC function is
available. Operating voltage range is 9.0 to 17.0 VDC.