ABS and EBS warning lamps are designed to alert the driver when a braking-system fault has been detected. They should never simply become part of the normal dashboard display because they have been illuminated for some time.
The action required depends not only on the warning displayed, but also on when the fault is identified. A warning discovered during a pre-use check must be reported and assessed before the vehicle enters service. If a warning develops during a journey, the driver must respond according to the nature and severity of the warning.
What Is the Difference Between ABS and EBS?
ABS stands for Anti-lock Braking System and is primarily designed to prevent wheel lock during braking.
EBS stands for Electronic Braking System. It is a broader electronically controlled braking system used on modern HGVs and trailers and incorporates anti-lock braking functionality alongside other braking and stability functions.
Older ABS-only vehicles and trailers may use different warning arrangements from modern EBS-equipped vehicles. Where the meaning of a particular warning is unclear, the vehicle manufacturer’s information should be consulted.
Amber or Yellow EBS Warning Lamp
On an EBS-equipped vehicle or trailer, an amber or yellow Malfunction Indicator Lamp (MIL) indicates that an electronic fault has been detected within the braking system.
“The amber/yellow lamp illuminates if there is an electronic fault”
If an amber or yellow warning is already present during the driver’s pre-use check, the defect should be recorded and reported through the operator’s defect-reporting procedure and appropriately assessed before the vehicle enters service. The fact that DVSA may categorise the defect as a delayed prohibition should not be interpreted as automatic permission to begin a journey with a known braking-system fault.
If an amber or yellow EBS warning develops during a journey, it should not be ignored. The driver should stop when it is safe to do so, report the defect and obtain appropriate technical or management advice so that the fault can be assessed and early rectification arranged.
Under the DVSA Categorisation of Vehicle Defects, a yellow EBS MIL illuminated is categorised as a delayed prohibition, with early rectification advised.
The DVSA Guide to Maintaining Roadworthiness describes a delayed-defect concession for roadside inspection in defined circumstances. This includes evidence that the defect occurred during the current day’s journey, that the vehicle was clear of defects at the beginning of the journey, and an in-service driver defect report containing a recorded assessment that the vehicle is safe to drive for the remainder of the current day’s journey.
Red EBS Warning Lamp
A red EBS warning is significantly more serious. The DVSA HGV Inspection Manual states that the red EBS MIL illuminates where there is a foundation-brake fault or where the prescribed minimum braking performance cannot be achieved.
“The red MIL illuminates if there is a foundation brake fault or the prescribed minimum brake performance cannot be met.”
If a persistent red EBS warning is identified during a pre-use check, the journey should not commence. The defect should be reported immediately and the vehicle should not enter service until the fault has been appropriately assessed and rectified.
If the red EBS warning remains illuminated or flashes after the normal system start-up sequence while the vehicle is in use, the driver should stop at the next safe location and not continue the journey. The defect should be reported immediately and the vehicle should not continue in service until the fault has been assessed and it has been established that the vehicle is safe to move.
At roadside inspection, an illuminated red EBS MIL is categorised by DVSA as an immediate prohibition. The current DVSA Categorisation of Vehicle Defects, Section 38, records “any red MIL illuminated” with action “I” (immediate prohibition), while a yellow MIL illuminated is recorded with action “D” (delayed prohibition).
Older ABS-Only Systems
Older ABS-only vehicles and trailers may use different warning arrangements from those found on modern EBS-equipped vehicles. Some trailers may use a separate ABS warning lamp or a trailer-specific warning displayed in the towing vehicle.
An illuminated or abnormal ABS warning indicates that the anti-lock braking system may not be operating correctly and should be treated as a defect. DVSA categorisation can depend on the braking-system configuration, so it should not be assumed that every ABS warning is treated in exactly the same way as an EBS warning.
The DVSA Categorisation of Vehicle Defects distinguishes between ABS faults according to the system fitted and, in some cases, whether load sensing is provided in addition to ABS.
Driver Action at a Glance
- Warning present before departure: Record and report the defect and have it appropriately assessed before the vehicle enters service.
- Persistent red EBS warning before departure: Do not commence the journey.
- Amber/yellow EBS warning develops during a journey: Stop when safe, report the defect and obtain appropriate advice so that the fault can be assessed and early rectification arranged.
- Red EBS warning develops during a journey: Stop at the next safe location, report the defect immediately and do not continue the journey.
A warning should never be ignored simply because the vehicle appears to brake normally or because the lamp has previously remained illuminated without an obvious problem.
Roadside Enforcement and DVSA Guidance
If an HGV or trailer is inspected by DVSA with an ABS or EBS fault present, the enforcement outcome will depend on the system fitted and the nature and severity of the defect.
A delayed prohibition allows a vehicle to continue operating for a limited period before the prohibition takes effect, giving the operator time to rectify the defect. GOV.UK states that an operator may have up to 10 days to have a defect fixed, after which the vehicle must be reinspected and the prohibition removed before it can be driven again.
An immediate prohibition takes effect straight away and can prevent the vehicle from continuing until the defect is rectified.
Source: GOV.UK – Roadside checks for commercial drivers: roadside prohibitions
The DVSA Categorisation of Vehicle Defects provides guidance on the categorisation of defects found during roadside inspections and vehicle tests. The HGV Inspection Manual separately defines the inspection processes and standards used during statutory HGV examinations, including the operation of ABS and EBS warning systems.
