11
Introduction
3.3.5
Deep Snow and Mud Switch
A deep snow and mud option switch is included with ATC. This function increases available traction on extra
soft surfaces like snow, mud or gravel, by slightly increasing the permissible wheel spin.
Drivers use a deep snow and mud switch to select this feature. When this function is in use, the ATC
indicator lamp blinks continuously.
3.3.6
How ESC Works
If a vehicle becomes unstable, this intelligent system automatically intervenes to reduce rollover, skidding
and jackknifing risk. The system detects instability through the use of onboard sensors measuring vehicle
dynamics and selectively applies foundation braking to correct vehicle heading and/or prevent rollover.
3.3.7
How HSA Works
Hill Start Aid (HSA) supports select automated manual transmissions in reducing/totally eliminating the
rolling back of the vehicle while launching on a grade. When requested from the transmission, HSA holds
pressure in the service brakes of all axles of the towing vehicle when the vehicle is standing still. HSA will
hold pressure for a maximum of three seconds following full release of the brake pedal. Communication
between the transmission and the ECU takes place via the J1939 data link.
HSA grade threshold parameters may be modified in the Transmission ECU. These parameters must be
reviewed with the transmission manufacturer prior to making any modifications in order to ensure safe
operation.
3.3.8
System Layout
A typical WABCO SmartTrac™ hydraulic ABS installation is illustrated below.
4011783a
ABS SENSOR CABLE
MASTER
CYLINDER
FRONT OF
VEHICLE
SENSOR
ASSEMBLY
HYDRAULIC
BRAKE LINE
ABS
MODULATOR
ASSEMBLY
ECU
BRAKE
BRAKE
BRAKE
BRAKE
HYDRAULIC BRAKE LINE
The ABS modulator assembly must be mounted below the master cylinder and above the brake calipers
and wheel cylinders.
