ALL-SPEED TRACTION CONTROL
The traction control system that is part of the Elec-
tronic Stability Program (ESP), is an all-speed traction
control. All-Speed Traction Control enhances mobility
and prevents wheel slip when accelerating on slippery
surfaces. It also provides a measure of directional sta-
bility control. Using the wheel-speed sensors, it can
detect excessive yaw and help keep the car on the
intended course, as for instance, when accelerating
around a curve.
All-Speed Traction Control is effective up to 85 mph
(137 km/h).
The traction control system may be turned off or on by
depressing the ESP Off switch button located on the
instrument panel.
ELECTRONIC VARIABLE BRAKE PROPORTIONING
Vehicles equipped with ABS use Electronic Variable Brake Proportioning (EVBP) to balance front-to-rear braking.
The EVBP is used in place of a rear proportioning valve. The EVBP system uses the ABS system to control the slip
of the rear wheels in partial braking range. The braking force of the rear wheels is controlled electronically by using
the inlet and outlet valves located in the Integrated Control Unit (ICU).
EVBP activation is invisible to the customer since there is no pump motor noise or brake pedal feedback.
OPERATION
ANTILOCK BRAKE SYSTEM
The following information applies to both antilock brakes (ABS) without Electronic Stability Program (ESP) and trac-
tion control and ABS with ESP and traction control.
ABS
There are a few performance characteristics of the Antilock Brake System (ABS) that may at first seem abnormal,
but in fact are normal. These characteristics are described below.
NORMAL BRAKING
Under normal braking conditions, the ABS functions the same as a standard base brake system with a diagonally
split master cylinder and conventional vacuum assist.
ABS BRAKING
ABS operation is available at all vehicle speeds above 3–5 mph (5–8 km/h) If a wheel locking tendency is detected
during a brake application, the brake system enters the ABS mode. During ABS braking, hydraulic pressure in the
four wheel circuits is modulated to prevent any wheel from locking. Each wheel circuit is designed with a set of
electric solenoids to allow modulation, although for vehicle stability, both rear wheel solenoids receive the same
electrical signal. Wheel lockup may be perceived at the very end of an ABS stop and is considered normal.
During an ABS event, the Integrated Control Unit (ICU) regulates hydraulic pressure at all four of the vehicle’s
wheels.
The hydraulic pressure at each front wheel is controlled independently (relative to the amount of slip at each wheel)
in order to maximize the braking force generated by the front brakes. The rear wheels are controlled such that the
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BRAKES - ABS SERVICE INFORMATION
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