wheel AUDI A4 1998 B5 / 1.G Brakes Description Of Systems Workshop Manual

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Description of systems

The individual components have the
following functions:

ABS

Anti-lock Brake System
ABS prevents the wheel from locking up during
hard braking initiated by the driver. Despite high
brake effectiveness, lane stability and steering
capacity are maintained.
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EDL

Electronic Differential Lock
The Electronic Differential Lock (EDL) is a
traction control aid for driving away from a
standstill. An electronically-controlled brake
application at the wheel that is spinning provides
a torque reaction point for the differential. This
enables the wheel with better traction to make
use of the engine power. EDL is effective in both
forward and reverse.
EDL is part of the basic configuration of vehicles
with All Wheel Drive (AWD). Although EDL only
regulates the front wheels on vehicles with Front
Wheel Drive (FWD), EDL regulates all four
wheels on vehicles with All Wheel Drive (AWD).
This makes it possible to eliminate the driver
operated mechanical differential lock.
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Onset of EDL regulation is permitted up to a
speed of 40 km/h. The upper switch-off barrier
for already active EDL is 40 km/h for vehicles
with Front Wheel Drive (FWD), but 80 km/h for
vehicles with All Wheel Drive (AWD).
The hydraulic unit is equipped with suction
dampers. They improve pressure build-up in the
appropriate brake cylinders during EDL
regulation. The functional range of the pressure
relief valve in the hydraulic unit is 170 25 bar. To reduce the risk of brake overheating, EDL
regulation is not permitted above a specific brake
temperature. The temperature limit is defined in
the ABS control module (w/EDL) -J104-. The
control module determines the actual brake
temperature via an algorithm. If the algorithm
determines that the brakes have reached a
temperature below the temperature limit, the EDL
system becomes effective again. Function of the
vehicle brake system and ABS are not affected
by intervention in this system.
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ASR

Anti-Slip Regulation (ASR)
The ASR option is only available on Front Wheel
Drive (FWD) vehicles. Observe control module
coding for these vehicles. The function of ASR
requires an exchange of signals between the
ABS control module -J104-, the Engine Control
Module (ECM) and the Transmission Control
Module (TCM). The control modules
communicate with each other.

There are two communication systems at work:

- Data is transferred via several single wires.

- Data is transferred via the CAN-bus. The
CAN-bus only contains two lines. These
transfer all required data.

To determine which communication system is
transferring data, use the "Check control module
version" function and check the table "Control
module versions".
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ASR prevents the wheels being powered from
spinning during acceleration by reducing engine
load. It is active throughout the entire speed
range. The EDL and ASR functions work in
combination during vehicle acceleration.
ASR can be switched on and off by pressing the
traction control button in the center of the center
console. ASR is re-activated on its own when the
ignition is switched on. When the traction control
button is operated, the ASR indicator lamp lights
up in the instrument cluster. During adjustment
mode, the indicator lamp blinks three times per
second.
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ESP

Electronic Stabilization Program (ESP)
The Electronic Stabilization Program (ESP) is a
driving dynamics regulation system. It stabilizes
the vehicle both in understeer and oversteer
situations. ESP regulation includes the functions
of EBD, ABS, EDL and ASR. A special function
of ESP is that it can brake individual wheels.

ESP includes the functions of EBD, ABS, EDL
and ASR. The individual components have
the following functions:
The ASR and ESP functions can be switched on
and off using the ASR/ESP switch on the center
console. If the driver steps on the brake pedal,
the status of the ESP switch is ignored. When
braking, ESP is always active. When the ignition
is switched on, the ASR and ESP functions are
activated.
When switched off, the ASR/ESP indicator light
is lit up in the instrument cluster. During
adjustment mode, the indicator lamp blinks three
times per second.
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