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Safety Checks - ABS Valves


In this safety checks feature we offer some tips on how to approach safety checks on the anti-lock braking system (ABS). A methodical approach pays dividends.

In the same way as a safety check on the care and maintenance
of brake calipers and friction material are carried out, the same methodical approach can be applied to any associated
equipment.

Fault Memory

At the heart of the anti-lock braking system (ABS) is the control system, and interpretation of the fault memory is one area that requires a specific approach.

With the exception of some earlier systems that can offer a ‘blink code’, most modern systems now require a diagnostic
tool.

There has been an increase in dependence upon these tools, and it has almost become the norm to reach for this equipment when faced with a warning signal on a vehicle. As there is a danger of losing sight of the physical mechanical fault that may be causing the warning signal, a basic list of considerations should be observed when interpreting these faults.

Whether you are using an OEM tool or a generic aftermarket diagnostic tool, the displayed text is often just a guide, giving the technician information on the correct wheel or part of the system.

Next Steps

Depending on the fault, some steps can be taken even before
removing the wheel. A check for wheel-bearing play should be carried out, as excessive play can be contributory to an ‘air gap’ fault.

Ask yourself if the vehicle has recently been driven in heavy
rain. The hydraulic effect of road surface water on the sensor
can push it out of its retaining clip sufficiently to trigger the warning lamp.

On removing the wheel, a visual inspection of the pole wheel is good practice. Slight corrosion or loss of definition on the castellation can give a signal error back to the electronic control unit (ECU).

Also, check for signs of excessive heat. The tolerance built
into the sensors has a limit, and over-exposure to excessive brake disc heat can have a detrimental effect on the system and create a problem.

For further information on this topic please call 01274 681144 or email serviceadmin@arriva.co.uk