8
4. In response to a serial communications request from a
diagnostic tool.
5. During brake torque limiting to avoid overheating of the
brakes.
6. When certain diagnostic trouble code conditions are
detected.
Engine Torque Limiting (ETL) with Smart ATC
™
Traction Control
The EC-60
™
controller uses Engine Torque Limiting to control
drive axle wheel slip. This is communicated to the engine
control module (using J1939), and is available at all vehicle
speeds.
Bendix
®
Smart ATC
™
Traction Control
The EC-60
™
controller has an additional feature known as
Smart ATC
™
traction control. Smart ATC
™
traction control
monitors the accelerator pedal position (using J1939) to
help provide optimum traction and vehicle stability. By
knowing the driver’s intention and adapting the target slip of
the drive wheels to the driving situation, the Smart ATC
™
traction control allows higher wheel slip when the accelerator
pedal is applied above a preset level.
The target wheel slip is decreased when driving through a
curve for improved stability.
Disabling ATC Engine Control and Smart ATC
™
Traction
Control
ATC Engine Control and Smart ATC
™
traction control will
be disabled under the following conditions:
1. In response to a serial communications request from
an off-board tool.
2. At power-up until the ECU detects a service brake
application.
3. If the ECU receives a J1939 message indicating that
the vehicle is parked.
4. If the dynamometer test mode is active. This may be
accomplished via an off-board tool or the diagnostic blink
code switch.
5. When certain diagnostic trouble code conditions are
detected.
Optional ATC Off-Road Mode
In some road conditions, the vehicle operator may desire
additional drive wheel slip when ATC is active. The Premium
EC-60
™
controller has an optional control mode to permit
this desired performance.
The vehicle operator can activate the off-road function with
a switch on the dash panel. Alternately, a J1939 message
may be used to place the vehicle in this mode. The ATC
Indicator Lamp will flash continually to confirm that the off-
road ATC function is engaged.
To exit the ATC off-road mode, depress and release the
ATC off-road switch.
Drag Torque Control Functional Overview
Premium EC-60
™
controllers have a feature referred to as
drag torque control which reduces wheel slip on a driven
axle due to driveline inertia. This condition is addressed by
increasing the engine torque to overcome the inertia.
Drag torque control increases vehicle stability on low-traction
road surfaces during down-shifting or retarder braking.
Dynamometer Test Mode
WARNING: ATC must be disabled prior to conducting any
dynamometer testing. When the Dynamometer Test Mode
is enabled, ATC brake control and engine control along with
drag torque control are turned off. This test mode is used
to avoid torque reduction or torque increase and brake control
activation when the vehicle is operated on a dynamometer
for testing purpose.
The Dynamometer Test Mode may be activated by pressing
and releasing the diagnostic blink code switch five times or
by using a hand-held or PC-based diagnostic tool.
The Dynamometer Test Mode will remain active even if power
to the ECU is removed and re-applied. Press and release
the blink code switch three times, or use a hand-held or
PC-based diagnostic tool to exit the test mode.
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
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