What is Anti-Lock Braking System(ABS)?  

The Anti-Lock Braking Systems (ABS) is a four-wheel system that prevents wheel lock-up by automatically modulating the brake pressure during an emergency stop. By preventing the wheels from locking, it enables the driver to maintain steering control and to stop in the shortest possible distance under most conditions.

During normal braking, the ABS and non-ABS brake pedal feel will be the same.

During ABS operation, a pulsation can be felt in the brake pedal, accompanied by a fall and then rise in brake pedal height and a clicking sound.

Vehicles with ABS are equipped with a pedal-actuated, dual-brake system. The hydraulic system consists of the following:

1. ABS hydraulic control valves and electronic control unit
2. Power brake booster
3. Brake master cylinder
4. Necessary brake tubes and hoses

The anti-lock brake system consists of the following components:

1. Hydraulic Control Unit (HCU).
2. Anti-lock brake control module.
3. Front anti-lock brake sensors / rear anti-lock brake sensors.

Anti-lock Brake System (ABS) operates as follows:
When the brakes are applied, fluid is forced from the brake master cylinder outlet ports to the HCU inlet ports. This pressure is transmitted through four normally open solenoid valves contained inside the HCU, then through the outlet ports of the HCU to each wheel.

The primary (rear) circuit of the brake master cylinder feeds the front brakes.

The secondary (front) circuit of the brake master cylinder feeds the rear brakes.

If the anti-lock brake control module senses a wheel is about to lock, based on anti-lock brake sensor data, it closes the normally open solenoid valve for that circuit. This prevents any more fluid from entering that circuit.

The anti-lock brake control module then looks at the anti-lock brake sensor signal from the affected wheel again.

If that wheel is still decelerating, it opens the solenoid valve for that circuit.

Once the affected wheel comes back up to speed, the anti-lock brake control module returns the solenoid valves to their normal condition allowing fluid flow to the affected brake.

The anti-lock brake control module monitors the electromechanical components of the system.

Malfunction of the anti-lock brake system will cause the anti-lock brake control module to shut off or inhibit the system. However, normal power-assisted braking remains.

Loss of hydraulic fluid in the brake master cylinder will disable the anti-lock system.

The 4-wheel anti-lock brake system is self-monitoring. When the ignition switch is turned to the RUN position, the anti-lock brake control module will perform a preliminary self-check on the anti-lock electrical system indicated by a three second illumination of the yellow ABS wanting indicator.

During vehicle operation, including normal and anti-lock braking, the anti-lock brake control module monitors all electrical anti-lock functions and some hydraulic operations.

Each time the vehicle is driven, as soon as vehicle speed reaches approximately 20 km/h (12 mph), the anti-lock brake control module turns on the pump motor for approximately one-half second. At this time, a mechanical noise may be heard. This is a normal function of the self-check by the anti-lock brake control module.

When the vehicle speed goes below 20 km/h (12 mph), the ABS turns off.

Most malfunctions of the anti-lock brake system and traction control system, if equipped, will cause the yellow ABS warning indicator to be illuminated.

Rear Wheel ABS
Most light trucks and SUVs use a form of ABS known as Rear Wheel ABS. The Rear Wheel Anti Lock (RWAL) system reduces the occurrence of rear wheel lockup during severe braking by regulating rear hydraulic line pressure. The system monitors the speed of the rear wheels during braking

Answered by 24x7 Online at 6:22 PM on January 01, 2008

Anti-Lock Braking Systems (ABS) are designed to maintain driver control and stability of the car during emergency braking. Locked wheels will slow a car down but will not provide steering ability. ABS allows maximum braking to be applied while retaining the ability to 'steer out of trouble'. The operation of ABS can slightly reduce stopping distance in some cases like on wet road surfaces, but it can increase the stopping distance in others, as may be the case in deep snow or gravel.

An ABS system monitors four wheel speed sensors to evaluate wheel slippage. Slip can be determined by calculating the ratio of wheel speed to vehicle speed, which is continuously calculated from the four individual wheel speeds. During a braking event, the function of the control system is to maintain maximum possible wheel grip on the road - without the wheel locking - by adjusting the hydraulic fluid pressure to each brake by way of electronically controlled solenoid valves.

For passenger car applications, the majority of ABS components are often housed together in a single, under-hood mounted module.

Answered by Dev at 5:13 PM on December 31, 2007

An anti-lock braking system (ABS) (translated from German, Antiblockiersystem) is a system on motor vehicles which prevents the wheels from locking while braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and, in some situations, to shorten braking distances (by allowing the driver to hit the brake fully without skidding or loss of control).
for more info,check out d following linl-:
http://en.wikipedia.org/wik i/Anti-lock_braking_system

Answered by tarun at 12:50 AM on December 31, 2007

An anti-lock braking system (ABS) (translated from German, Antiblockiersystem) is a system on motor vehicles which prevents the wheels from locking while braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and, in some situations, to shorten braking distances (by allowing the driver to hit the brake fully without skidding or loss of control).

Answered by jasmeet at 11:34 PM on December 26, 2007