Diagnostics

EBS

The abbreviation EBS stands for Electronic Braking System. The purpose of this system is to improve

vehicle control, reaction and stability during braking over and above that currently possible from a

conventional pneumatic system. This is achieved by using electrical signals to operate pneumatic

valves. A back up system is usually retained in case of an electrical failure.

A great benefit with EBS is that it can simultaneously fulfil the operation of an anti-lock system (ABS)

and a load sensing system with a superior reaction time. If the vehicle is towing an EBS trailer the two

systems can communicate via a data bus and offer the potential of improved tractor/ trailer

compatibility. With motor vehicles it can also provide ASR (Anti-Slip Reduction).

Manufacturers claim:

Reduced combination response times

 Improved stability under braking

 Improved compatibility between vehicle and trailer

 Reduced operating temperatures

Reduction in components and pipework

 Reduced operating costs

 Improve even brake lining wear on motor vehicles

 Comprehensive self diagnostic tests

 Motor Vehicle ECU (Electronic Control Unit)

This unit controls and monitors the operation of the EBS. It maybe linked to other electronic

components through a CAN (Controlled Area Network) data line. In this way, whenever it receives a

signal from the Brake Signal Transmitter, it takes instant and continuous readings from the wheel

speed sensors on the vehicle. These figures can be used to calculate, in microseconds, the braking

deceleration that is required.

The ECU measures pressure at the wheels on all the different axles, bogies, or multiples of axles and

activates the modulator valves to maintain even and steady braking all round. When necessary the

same sensors also prompt the ABS and ASR (if fitted) intervention.

Static Roller Brake Testing

EBS is a permanently powered system.

Motor Vehicles

With the advancement of electronic controls the modulation of braking on the axles is highly dependent

on the imposed axle loads. During a roller brake test on a motor vehicle, which is not up to its design

weight, it may give an impression of poor brake performance. If this is the case depending on the

examining criteria i.e. for annual test purposes, it is possible the brake performance may not be

sufficient to meet the Goods Vehicles (Plating and Testing) Regulations (these Regulations compare

the braking effort produced to the design weights of the vehicle). For enforcement purposes the brake

performance should be measured against the presented weight as required by the Road Vehicles

(Construction and Use) Regulations.

For annual test purposes, in order to eliminate the modulating effect, it is acceptable (provided the

vehicle is within 65% of its design weight) to build the air pressure to maximum, switch ignition off,

release the parking brake and then conduct the brake test. The vehicle should be allowed to replenish

its air reservoirs after each application of the footbrake.