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You might think your car's braking system is relatively simple. However, with the advancement of technology, modern vehicles feature advanced braking systems that can prevent brakes from locking up as well as distribute brakeforce evenly to all four wheels.

In-car technology like electronic brakeforce distribution has progressed massively over the years, thanks to improvements in the processing speed of computers and huge improvements in the sensor technology that reads grip levels.

Often referred to as EBD, electronic brakeforce distribution now features on the majority of cars with ABS, including MG HS, and helps to improve driving experiences every day.

What is electronic brakeforce distribution (EBD)?

Electronic Brakeforce Distribution, or EBD, is a subsystem of the vehicle's anti-lock braking system and electronic stability control (ESC).

Put simply, EBD is a system that stabilises the amount of braking force on each wheel of the car. In doing this, electronic brakeforce distribution provides stronger and safer braking performance in emergency scenarios. The amount of pressure applied to each wheel can be varied due to factors such as the condition of the road or the speed of the vehicle.

EBD brakes are part of what is considered active safety equipment, as they help prevent a crash from occurring or lessen the impact of an accident.

How does electronic brakeforce distribution work?

The way that the electronic brakeforce distribution systems typically works is by looking at data from speed sensors to determine if any of the wheels aren't rotating at the same speed as the others. If a discrepancy is found, indicating that a tyre may be skidding, corrective measures can be taken.

The electronic brakeforce distribution system is part of a suite of braking and stability safety technologies and makes use of three components; the speed sensors, brake force modulators and electronic control unit (ECU).

Speed sensors

The speed sensor not only calculates the speed of the car, but the speed of the engine too (RPM). Electronic brakeforce distribution can be used when the speed of the wheel may not be the same as the speed of the car, which results in skidding. The speed sensors calculate the likelihood of the car losing control and relay this to the EBD system.

Electronic Control Unit

The electronic control unit collects the data from the speed sensors in each wheel and uses this data to calculate the slip ratio (difference between the speed of the car and the rotation of the tyre). Once the slip ratio is determined, it makes use of the brake force modulators to keep the slip ratio within limits.

Brake Force Modulators

The brake force modulators pump brake fluid into the brake lines and activate the brake cylinders. The brake force applied on each wheel can be controlled by the electronic brakeforce distribution system.

All these three components work in tandem and make the EBD system work flawlessly.

Electronic brakeforce distribution can also work by responding to differences in wheel weights, road conditions, or braking situations much faster than the driver can sense them. The system can also vary pressure on individual wheels - which the driver can't. This greatly improves braking performance.

What is the purpose of electronic brakeforce distribution?

The purpose of electronic brakeforce distribution is similar to that of anti-lock brakes and traction control - to stabilise the vehicle under heavy braking. These technologies are all designed to prevent the wheels of a vehicle from locking up, which can cause a driver to lose control very quickly. Unlike other brake systems, electronic brakeforce distribution is able to dynamically control the brake force that is applied to each wheel.

What happens if my electronic brakeforce distribution system fails?

In the event of your electronic brakeforce distribution system failing, the conventional brake system should continue to function normally. That means you'll typically be fine if you have to drive a vehicle that has a malfunctioning EBD system. However, you'll need to take extra care when braking and should call your local dealer as soon as you can.

Since EBD and ABS (AntiLock Braking Systems) use many of the same components, your anti-lock brakes will often fail at the same time as your electronic brake force distribution system, which means you may need to pump your brakes instead of applying steady pressure.

Manufacturers recommend that you check your brake fluid level if you suspect a malfunctioning electronic brakeforce distribution system, since some vehicles use the same warning light for low fluid that is used for other brake issues. If the fluid level is low, you should avoid driving the vehicle until it has been topped up, and a mechanic should inspect the system for leaks.

To find out more useful information on our safety features, take a look at our full list of car safety feature articles.

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What Is Electronic Brakeforce Distribution?

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You might think your car's braking system is relatively simple. However, with the advancement of technology, modern vehicles feature advanced braking systems that can prevent brakes from locking up as well as distribute brakeforce evenly to all four wheels.

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Further Guidance
Technical Information
ABS has been a common safety-related fitment to vehicles since the early 1980s with systems from ATE, Bosch and Bendix. The systems all have a similar operational strategy and are all electromechanical.

The ABS ECU (Electronic Control Unit) wants to see a continuous stream of sine waves for all four of the vehicle's wheels. If however the brakes are applied and a wheel locks, the ECU will lose the signal from that wheel. If the ECU sees this happen, it will immediately release the hydraulic pressure to the wheel in question and very quickly pulse the pressure within the hydraulic system to maximise braking efficiency.

A vehicle fitted with an ABS system has better braking abilities in adverse wet or slippery conditions. Some vehicles may have ABS fitted to only the front wheels of the vehicle.

The ABS sensors can also perform another role when the vehicle is fitted with traction control. Instead of looking for a loss of signal from a locked wheel the ECU looks for increased individual frequencies as an indication of wheels spinning, losing grip. If a spinning wheel is detected, the engine power output is reduced until all frequencies from the ABS sensors are the same and traction is regained. Some systems momentarily apply the brake to the spinning wheel to aid traction on the other wheel through differential action.

Figure 2 shows a typical front hub ABS set up, where the driveshaft has a series of teeth on it and the speed sensor is mounted close to them.

Figure 3 shows an alternative set up using a castellated drive ring mounted on the wheel bearing. The inductive sensor is the built into a hub cap located on the inside of the vehicle hub assembly.

There are several different connection methods, depending on whether you wish to look at an individual speed sensor or a pair of sensors. Also, you will need to decide if the sensor can be tested statically (with the vehicle on a wheel free lift) or while on road test. The test point will differ from one system to another. Some may have fly-lead multi-plugs with easy access, and on others the wiring may be routed into the inner wing or bulkhead in such a way that no connections can be made. In this case you may need to locate the ABS electronic control module and probe the wiring there. Technical data will be needed in order to ensure the correct connections are made the two sensor wires must be connected with the correct polarity for the correct signal is to be displayed on the oscilloscope.

If the wheel speed signals fall outside of normal parameters then the ABS function may be turned off. A driver warning light will be illuminated and as with any electrical fault on ABS, normal hydraulic braking is maintained.
Generic DTC's ABS Wheel Speed Sensors
C0035 - Left Front Wheel Speed Circuit Malfunction

C0040 - Right Front Wheel Speed Circuit Malfunction

C0041 - Right Front Wheel Speed Sensor Circuit Range/Performance (EBCM)

C0045 - Left Rear Wheel Speed Circuit Malfunction

C0046 - Left Rear Wheel Speed Sensor Circuit Range/Performance (EBCM)

C0050 - Right Rear Wheel Speed Circuit Malfunction

C0051 - LF Wheel Speed Sensor Circuit Range/Performance (EBCM)

C0221 - Right Front Wheel Speed Sensor Circuit Open

C0222 - Right Front Wheel Speed Signal Missing

C0223 - Right Front Wheel Speed Signal Erratic

C0225 - Left Front Wheel Speed Sensor Circuit Open

C0226 - Left Front Wheel Speed Signal Missing

C0227 - Left Front Wheel Speed Signal Erratic

C0229 - Drop Out of Front Wheel Speed Signals

C0235 - Rear Wheel Speed Signal Circuit Open

C0236 - Rear Wheel Speed Signal Circuit Missing

C0237 - Rear Wheel Speed Signal Erratic

C0238 - Wheel Speed Mismatch

C0245 - Wheel Speed Sensor Frequency Error

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Technical Information ABS has been a common safety-related fitment to vehicles since the early 1980s with systems from ATE, Bosch and Bendix. The systems all have a similar operational strategy and are all electromechanical. The ABS ECU (Electronic Control Unit) wants to see a continuous stream of sine waves for all four of the vehicle's wheels.

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This video shows you the basics on how ABS works, the difference between vehicles with ABS and with out and also the key components to make ABS work