Bendix Commercial Vehicle Systems GEN 5 ABS - Manual (Page 4)

4
FIGURE 4 - ATC Indicator Lamp
Automatic Traction Control (ATC) System
The ATC system is available on all Standard ABS ECU’s.
ATC is not available on Basic ECU’s. It helps improve
traction on slippery or unstable driving surfaces by
preventing excessive wheel spin. ATC also enhances
vehicle stability by prevention of power spin-out.
ATC requires:
1. ATC valve - Either a stand alone valve or a Rear Axle
Valve Assembly with integral ATC solenoid may be used.
2. SAE J1922 or J1939 engine interface (the ABS ECU
serial data interface must match the engine controller
interface).
3. Brake Light Switch input.
4. ATC Indicator Lamp.
The Electronic Control Unit (ECU) must be configured for
ATC operation either by using the diagnostic switch, an
MPSI ProLink
® hand-held tester or Eaton’s ServiceRanger
PC software.
ATC Operation
During periods of wheel slip, the Electronic Control Unit
enters an Automatic Traction Control mode. There are
various modes of Automatic Traction Control.
System operation:
• At speeds above 25 mph, the engine is throttled back
via the SAE J1922 or SAE J1939 data link to control
spin out.
• At speeds below 25 mph, both engine control and
differential brake control are activated as required to
control wheel slip. Once triggered, differential braking
mode remains active regardless of vehicle speed.
• An optional mud and snow switch allows greater wheel
spin (more torque) when activated. It is intended for
adverse conditions, usually off-highway. Except for
special cases, the switch is programmed for momentary
operation. ATC reverts to normal operation when the
switch is cycled a second time and whenever the system
goes through a power-up cycle.
Component Function
When brake control is utilized, the ATC valve is activated,
diverting supply tank air to the Modulator Valves on the
drive axle(s). The Electronic Control Unit then activates
the appropriate solenoids in order to apply a brake force to
the spinning wheel. The Automatic Traction Control System
cannot increase traction to a particular wheel; it can only
utilize the available traction.
Thermal (Brake Heat) Protection
To prevent excessive brake and drum temperature resulting
from brake activity, ATC incorporates a brake temperature
estimation algorithm to determine when differential braking
mode should be suspended. The differential braking
function is re-enabled after a cool-down period.
ATC Indicator Lamp
The ATC indicator lamp operates when a vehicle is
equipped with the optional Automatic Traction System.
• Gen 4 ™ ABS – Lights at key-ON and remains lit with
ATC inactive until the driver presses the brake pedal.
• Gen 5 ™ ABS – Lights at key-ON and turns off after a 2
second lamp check. ATC is active after the lamp check.
• Flashes rapidly to indicate that ATC is active.
• Flashes slowly when the “mud-and-snow” mode is
selected and then flashes more rapidly when the
automatic traction control system operates.
• Remains ON if an engine data link failure occurs.
NOTE: Some non-ATC equipped vehicles have an ATC
lamp that is labeled as a spin light. It indicates when a low
traction condition has been encountered. No control action
is taken.