ABS System Parts You Should Be Aware Of

What Is The Purpose Of ABS In A Vehicle? Why Do You Need ABS?

As the brakes are applied by the driver, the rotation of the wheels is stopped, but the momentum of the vehicle still remains which causes the vehicle to continue moving even after the wheels have stopped. This is due to the inertia of the vehicle that causes the vehicle to maintain its movement while the wheels get locked-up due to the braking action and causes the car to skid. A locked-up wheel starts skidding and has no traction (grip of the tires with the road) as compared to a non-skidding wheel since the skidding wheel simply glides over the ground surface. 

This is really dangerous since high-speed braking can cause loss of traction and the driver can lose steering control over the vehicle. Hence it becomes imperative to have a way of maintaining traction while braking and gain control over the vehicle. This is done by employing a system called Anti-Lock Braking System (ABS) which prevents the locking up of the wheels and retains control over the vehicle during braking. 

ABS System Parts

The ABS prevents wheel lock-up and retains steering control and traction between the tires and ground surface and decreases stopping distance on dry and slippery surfaces. It does so by monitoring the speed of the wheels and altering the brake pressure applied at the wheels to effectively stop the wheels along with the vehicle and avoid wheel slippage and vehicle skidding. 

The ABS mainly consists of four elements - Sensors, Valves, ECU and HCU. 

  • Sensors: Wheel speed sensors monitor the realtime speed of the wheels. This way the sensors can monitor any sudden changes in the speed of each wheel - either very quick deceleration or acceleration. They also monitor the rate at which deceleration takes place.
  • Valves: These control the amount of brake or hydraulic pressure applied to the brake unit. There are three variations - In the first position, the brake valve is open and it allows the pressure from the master cylinder to be transferred to the brakes. In the second position, the brake valve remains closed and pressure from the master cylinder to the brakes is restricted. In the third position, the valve releases some of the pressure to the brakes.
  • ECU: This is an electronic control unit that operates the ABS system. The data from the sensors is analyzed by the ECU and calculates the wheel rotational speed and acceleration/deceleration. It also alters the brake pressure via the HCU.
  • HCU: The hydraulic control unit (HCU) consists of a pump and accumulators. It receives signals from the ECU to alter the brake pressure applied to the brakes. In case of low pressure, the pump is actuated to apply the required pressure to maintain effective braking. 

How Does ABS Work?

The ABS works by monitoring the speed of each wheel compared to other wheels and also the rate at which deceleration of each wheel takes place. While braking the speed of the wheel is different from that of the vehicle. That is what causes the wheels to drag, skid or slide across the road instead of rolling and results in loss of control of the vehicle. 

When the brake pedal is depressed by the driver, the wheels receive hydraulic pressure through the ABS valves which is then transmitted to the brakes. The valve consists of solenoids that are connected to the ABS ECU. This allows the ECU to actuate the valve and control the flow of the pressure. The ABS sensor monitors the speed of the wheel and the rate of deceleration and determines whether the wheel is about to lock up and releases the brake pressure by cutting off supply from the valve. 

Then it monitors the acceleration of the wheel and reapplies the brakes using the hydraulic pump pressure. It does this cycle around 15 times a sec. This procedure allows the wheel to retain its grip on the ground by maintaining the wheel in a position where the braking effect is maximum (which is right before the wheel locks-up). Doing this allows the driver to steer the vehicle since the traction is still present at the tires and allows control over the vehicle. The stopping distance of the vehicle is also reduced since skidding is prevented. 

Symptoms Of ABS System Failure

The ABS system on most modern cars combines hydraulics, electronics and mechanical components and so the likelihood of failure is quite high. The most commonly replaced ABS system parts include wheel speed sensors, ABS valves and hydraulic pumps. 


ABS Warning Light

The first and most obvious sign of ABS failure is a warning light in the dashboard. ABS warning lights usually occur when there is an electrical issue with the system like a broken wheel speed sensor or faulty ABS control module. A diagnostic tool can help you discover the underlying problem. However, older vehicles having earlier ABS systems usually don’t have a dedicated ABS warning light and so share the “Check Engine” light. It is always wise to investigate an ABS warning light since the issue can be a simple wiring problem or trouble with the ABS module. 

Unresponsive Brake Pedal

If depressing the brake pedal yields no result then there is a definite issue with either the ABS or brake system. This issue usually develops over time and you might notice a gradual decrease in braking response, that eventually ceases completely and results in an unresponsive brake pedal. The problem may arise due to clogged ABS hydraulic valves, broken brake lines, faulty brake master cylinder or a leak in the brake hydraulics. Have your vehicle ABS and brake system inspected immediately before the damage gets worse. 

Increased Brake Pedal Effort 

The brake pedal is supposed to feel firm but the braking response should also be immediate and constant. A variation in the brake pedal feel or a noticeable increase in the amount of force required to brake can be a sign of ABS system failure. This can be caused by either a malfunctioning ABS module or a failing ABS pump. If left unchecked the brakes in the vehicle can be completely compromised. Have your vehicle inspected asap. 

Brakes Locking

The ABS system is intended to prevent wheel and brake locking up and so in the event of its failure, you can expect those issues to occur. Wheel locking causes the vehicle to skid and diminishes traction of the tires with the ground surface. This means the vehicle will take significantly longer to stop and the driver will also have no steering control while braking. If your ABS system is acting up then you may notice the vehicle takes much longer to stop and the brakes lock up even during normal driving conditions. These issues can occur due to a bad ABS control module or ECU. Also inspect the brake callipers and brake pads for any sticking issues. 

The ABS system in your vehicle is extremely important safety equipment which needs to be kept in proper working condition for safe and efficient driving and braking experience. In case you notice issues with the ABS system then have it inspected and replace any faulty components to restore the system to its factory state. You can actively take measures to ensure the ABS and brake system components last longer


Q) Is It Safe To Drive With ABS Disabled?

ABS is a critical safety feature. Driving with ABS disabled can dramatically decrease the braking performance of the vehicle under high-speed braking. The vehicle also becomes susceptible to hydroplaning when driving over wet surfaces and the possibility of skidding is much higher. The bottom line is that driving with ABS disabled is a very bad idea and there is a definite reason why it is installed by manufacturers and even mandated by law (as standard equipment) in certain countries. 

Q) How Do You Know If ABS Is Working?

When the ABS is working properly, the driver can notice a certain pulsation action from the brake pedal while braking. This can also be accomplished by grinding and buzzing noises which simply means the ABS system parts are at work. The brake pedal pulsates as the hydraulic pressure within the brake lines is moderated by the ABS system. If you feel this happening then do not let go of the brake pedal as it only means the ABS is working. 

Q) Will Brakes Still Work Without ABS?

While ABS is not vital for breaking it still is a significant safety feature that is standard on most vehicles today. The brakes can be applied without ABS functioning but you will lose control over the vehicle under heavy braking scenarios since the vehicle will skid and the wheels will lock up which increases stopping distances and disables steering. 

Q) At What Speed Does ABS Work?

The ABS only works when braking from speeds above 25 km/p (12 - 15 mph). At lower speeds, the wheels do not suffer locking and so ABS functionality becomes redundant.