One in Four Drivers Has Urgent Dashboard Warning Light – Will It Fail an MOT?

One in four motorists is reportedly driving with an urgent dashboard warning light illuminated, while more than a quarter admit they have a poor understanding of what their car’s warning lights actually mean.

The findings raise an important question for millions of motorists approaching their next MOT: can an illuminated dashboard warning light cause your car to fail?

The answer is yes — some warning lights can result in an MOT failure.

But not every illuminated symbol on a dashboard automatically means a failed MOT. It depends on the warning light, the vehicle and whether it indicates a malfunction covered by the MOT inspection.

One in four motorists driving with urgent warning lights

The research, commissioned by Halfords and based on a poll of 2,000 UK drivers, found that 25% were driving cars displaying an urgent dashboard warning light.

It also found that 28% admitted having a poor understanding of the warning lights displayed by their vehicle.

More concerning for garages, 14% said they had ignored warnings and avoided taking their vehicle to a garage for servicing, maintenance or repairs because of the cost and inconvenience involved.

The research also found that some motorists delay dealing with problems until they become more serious.

According to the survey, 44% admitted waiting until an issue became “serious”, with the resulting delay contributing to an average repair bill of £190.

Around one in five of those avoiding garages said they knew somebody who could repair the vehicle for them and therefore chose not to use a professional mechanic.

Whatever the reason for delaying repairs, motorists should not assume that an illuminated warning lamp can safely be ignored.

The Highway Code advises drivers to understand the warning displays on their vehicle and warns that they can indicate a serious fault developing.

Which dashboard warning lights are checked during an MOT?

Dashboard warning lamps form part of the MOT inspection where the relevant system and vehicle requirements apply.

According to official government guidance, malfunction indicator lamps or dashboard warning lights checked during an MOT can include those associated with:

• anti-lock braking systems (ABS)
• electronic stability control (ESC)
• airbags and supplementary restraint systems (SRS)
• seatbelt pretensioners and load limiters
• electronic parking brakes
• brake fluid
• electronic power steering
• tyre pressure monitoring systems (TPMS)
• engine and emissions systems

Whether an illuminated lamp results in a failure depends on the particular system, vehicle and applicable MOT requirement.

Here are some of the warning lights motorists should pay particular attention to.

ABS warning light

An illuminated ABS warning light can cause an MOT failure.

The MOT inspection includes anti-lock braking systems where the requirements apply to the vehicle.

If the ABS warning device indicates a system malfunction, it is classed as a Major defect.

That means the vehicle fails its MOT.

An illuminated ABS lamp can indicate a range of problems, potentially including faults involving wheel-speed sensors, wiring or other components within the system.

Drivers should therefore have the fault diagnosed rather than simply trying to extinguish the warning lamp before the MOT.

Airbag and SRS warning light

An airbag or supplementary restraint system warning light can also cause an MOT failure.

The DVSA MOT inspection manual states that an SRS malfunction indicator lamp indicating a system malfunction is a Major defect.

This is different from a lamp simply indicating that a passenger airbag has deliberately been switched off.

DVSA specifically states that a lamp illuminated to show that the passenger airbag is disabled should not itself be regarded as a defect.

The distinction is therefore between a genuine system malfunction and the normal operation of a vehicle feature.

Electronic stability control warning light

Electronic stability control — variously described by manufacturers as ESC, ESP, DSC or other names — is another system covered by the MOT where applicable.

A warning lamp indicating an ESC malfunction is classed as a Major defect.

However, testers need to establish that the lamp really is indicating a malfunction.

Some vehicles allow the stability-control system to be switched off manually, and the warning indication associated with that isn’t necessarily the same as a fault.

The MOT manual tells testers they should only fail a vehicle when they are certain that the warning lamp indicates an ESC malfunction.

Engine management light

The engine management light — sometimes known as the check-engine light or engine malfunction indicator lamp (MIL) — can also be relevant to the MOT.

The MOT inspection manual includes the engine MIL within the emissions section of the test.

For vehicles to which the relevant requirement applies, an engine MIL that is inoperative or indicating a malfunction is classed as a Major defect.

The underlying cause can range from sensor and emissions-control problems to more significant engine-management faults.

An illuminated engine management light should therefore be investigated before an MOT rather than assuming the car will pass because it appears to drive normally.

Electronic power steering warning light

Electronic power steering is another area where a warning lamp can matter.

Where the relevant MOT requirements apply, an electronic power steering malfunction indicator lamp indicating a system malfunction can result in a Major defect.

Power-steering faults can also potentially affect the safety and handling of the vehicle, making an illuminated warning lamp something motorists should investigate regardless of when their next MOT is due.

TPMS warning light

Tyre pressure monitoring systems are slightly different.

Vehicles first used on or after 1 January 2012 are subject to MOT requirements relating to the tyre pressure monitoring system.

Under the current MOT inspection manual, a TPMS that is malfunctioning or where a tyre is obviously under-inflated is classified as a Minor defect.

However, a TPMS that is obviously inoperative is classified as a Major defect.

Again, the warning lamp needs to be considered alongside the condition and operation of the system rather than treating every illuminated tyre symbol in exactly the same way.

Brake warning lights

Brake-related dashboard warnings should never simply be ignored.

The MOT includes requirements covering ABS, electronic braking systems, electronic parking brakes and brake-fluid warning systems where applicable.

The exact MOT outcome depends on the warning indication and the vehicle’s braking system, but some brake-system warning faults are classified as Major defects.

More importantly, an illuminated brake warning lamp can potentially indicate a safety-critical problem.

A motorist concerned about the operation of their brakes should have the vehicle inspected rather than waiting for the MOT to identify the problem.

Does every dashboard warning light mean an MOT failure?

No.

This is an important distinction.

Modern vehicles can display dozens of warning, information and status messages.

Not every illuminated dashboard symbol forms part of the MOT and not every warning message automatically constitutes a defect.

DVSA guidance covering supplementary restraint systems, for example, specifically notes that warning messages shown on dashboard displays are not defects in their own right, although they may help an MOT tester determine whether a malfunction exists.

The MOT is concerned with the systems and defects included within the official inspection requirements.

So the fact that a vehicle displays a warning does not necessarily mean it will fail.

Equally, motorists should not assume a warning can safely be ignored simply because it isn’t an MOT failure item.

Red, amber and green warning lights

Dashboard warning colours can provide an indication of urgency, although motorists should always consult the handbook for their particular vehicle.

Red warning lights commonly indicate faults or conditions requiring immediate attention.

Amber warning lights generally indicate something that requires investigation or monitoring.

Green and blue lamps are more commonly informational, showing that a system or function is operating.

There are variations between manufacturers, however, and increasingly sophisticated digital instrument displays mean the precise message presented to drivers can differ substantially between vehicles.

The owner’s handbook remains the best reference for understanding what a particular warning symbol means.

Don’t simply clear warning lights before an MOT

Modern diagnostic equipment can read and clear fault codes stored by a vehicle’s electronic control systems.

But simply extinguishing a warning lamp does not necessarily repair the fault that caused it.

If the underlying problem remains, the warning may return.

For garages, this creates an opportunity to explain the difference between fault-code diagnosis and simply clearing a dashboard warning.

Proper diagnosis should identify why the vehicle has generated the fault before deciding what repair is required.

The growing complexity of vehicle electronics also means diagnostic capability is becoming increasingly important for independent garages.

Warning lights can prevent bigger repair bills

One of the more interesting findings from the Halfords research is that some motorists deliberately postpone visiting a garage.

Cost is understandably an important consideration for drivers, particularly when household budgets are under pressure.

But ignoring a warning can sometimes allow a relatively straightforward fault to develop into something considerably more expensive.

Warning lamps exist because the vehicle has detected something the driver needs to know about.

That doesn’t mean every illuminated symbol represents an immediate catastrophe.

It does mean motorists should establish what the warning means rather than hoping it disappears.

Check dashboard warning lights before the MOT

Checking the dashboard should be part of a driver’s basic pre-MOT preparation.

When the ignition is switched on, various warning lamps normally illuminate as part of the vehicle’s self-check procedure before going out.

A warning lamp that fails to illuminate when it should, remains illuminated after starting or appears while driving can indicate a fault.

Motorists approaching their MOT should therefore pay attention to:

• ABS warning lights
• airbag or SRS warnings
• ESC or stability-control warnings
• engine management lights
• electronic power-steering warnings
• TPMS warnings
• brake-system warning lights

If any remain illuminated unexpectedly, getting the vehicle checked before presenting it for an MOT could avoid a failed test — and potentially identify a safety problem before it becomes more serious.

The key message is simple: not every dashboard warning light automatically means an MOT failure, but some definitely can.

And regardless of the MOT result, an urgent warning from the vehicle itself shouldn’t simply be ignored.

Sources

Halfords — Dashboard warning lights explained
https://www.halfords.com/car-repairs/advice/dashboard-lights.html

GOV.UK — Car parts checked at an MOT
https://www.gov.uk/government/publications/car-parts-checked-at-an-mot/car-parts-checked-at-an-mot

DVSA — MOT inspection manual for cars and passenger vehicles
https://www.gov.uk/guidance/mot-inspection-manual-for-private-passenger-and-light-commercial-vehicles

DVSA — MOT inspection manual: Other equipment, including SRS and ESC
https://www.gov.uk/guidance/mot-inspection-manual-for-private-passenger-and-light-commercial-vehicles/7-other-equipment

GOV.UK — Highway Code: vehicle maintenance, safety and security
https://www.gov.uk/guidance/the-highway-code/annex-6-vehicle-maintenance-safety-and-security