User's Manual

11
ATC OPERATION
ATC Functional Overview
Just as ABS improves vehicle stability during braking,
Automatic Traction Control (ATC) improves vehicle stability
and traction during vehicle acceleration. The Bendix
®
ESP
®
EC‑80
™
Controller's ATC function uses the same
wheel speed information and modulator control as the
ABS function. The Bendix ESP EC‑80 Controller detects
excessive drive wheel speed; compares the speed to the
front, non‑driven wheels; and reacts to help bring the wheel
spin under control. The Controller can be congured to use
engine torque limiting and/or differential braking to control
wheel spin. For optimal ATC performance, both methods
are recommended.
ATC/ESP Lamp Output/ATC Mud/Snow Switch
Input
Bendix ESP EC‑80 Controllers operate the ATC/ESP dash
lamp as follows.
The ATC/ESP dash lamp illuminates:
1. During power up (e.g. when the vehicle is started) for
approximately 2.5 seconds and turns off after the self
test is completed, providing no Diagnostic Trouble
Codes (DTCs) are present.
2. When ESP or ATC is disabled for any reason.
3. During an ESP or ATC event (the lamp will ash rapidly
at a rate of 2.5 times per second).
4. When the ECU is placed in the ATC off‑road mode
(the lamp will ash steadily at a rate of once every 2.5
seconds). This noties the vehicle operator that the
ATC Mud/Snow mode is active.
5. When the ECU is placed in the ABS off‑road mode.
When in this mode, ESP will be disabled below 25 mph
and its inactive status will be indicated by a steadily
illuminated ATC/ESP lamp.
Differential Braking
Differential braking within ATC is automatically activated
when drive wheel(s) on one side of the vehicle are spinning
excessively. This typically occurs on road surfaces
with patches of ice. The traction system will then lightly
apply the brake to the drive wheel(s) that are spinning
excessively. The vehicle differential will then drive the
wheels on the other side of the vehicle.
Differential braking (as part of ATC functionality) is available
at vehicle speeds up to 25 mph/40 kph.
Disabling ATC Differential Braking
ATC differential braking is disabled under the following
conditions:
1. During power up (e.g. when the vehicle is started), until
the ECU detects a service brake application.
2. If the ECU receives a J1939 message indicating that
the vehicle is parked.
3. When the dynamometer test mode is active. The
Dynamometer test mode is entered using the diagnostic
Blink Code Switch or by using a diagnostic tool (such
as Bendix
®
ACom
®
Diagnostics).
4. In response to a serial communications request from
a diagnostic tool.
5. If ATC Differential Braking function is activated for a
long time period to avoid overheating of the brakes. It
would take approximately three (3) continuous minutes
of activation for the time‑out to occur. Once timed‑out,
approximately two (2) minutes of "cool off" time would
be required before ATC Differential Braking can be used
again.
6. When certain DTC conditions are detected.
Traction Control with Engine Torque Limiting
The Bendix ESP EC‑80 Controller uses Engine Torque
Limiting to control drive‑axle wheel slip. This is commu‑
nicated to the engine control module (using J1939), and
is available at all vehicle speeds.
Bendix
®
SMART ATC
™
System
The Bendix ESP EC‑80 Controller has an additional feature
known as the Bendix
®
SMART ATC
™
system. This system
monitors the accelerator pedal position (using J1939)
to help provide optimum traction and vehicle stability.
By determining the driver’s throttle input and adapting the
target slip of the drive wheels to the driving situation, the
Bendix SMART ATC system allows higher wheel slip when
the accelerator pedal is applied above a preset level.
The wheel slip allowed by the Bendix SMART ATC system
is decreased when driving through a curve for improved
stability.
Disabling ATC Engine Control and the Bendix
SMART ATC System
ATC Engine Control and the Bendix SMART ATC system
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; or
5. When certain DTC conditions are detected.