What Should You Do When a Dashboard Warning Light Comes On?
Start with the colour, but do not stop there. Look at whether the light is steady or flashing, what symbol is showing, whether a dashboard message appears and what the car is doing at the same time. A warning light is evidence that helps you decide the next check; it is not always the complete diagnosis.
Red warnings usually need the fastest response, amber warnings normally mean a system needs attention, and green or blue lights are commonly status indicators. However, a flashing light, loss of braking, heavy steering, overheating, misfiring, smoke or sudden power loss can make the situation much more urgent regardless of colour.
🟥 Red
Stop / InvestigateRed lights can indicate problems involving oil pressure, overheating, braking, charging or other systems that may become unsafe or cause expensive damage if ignored.
🟠 Amber / Yellow
Diagnose SoonAmber often means the car has detected a fault or a system needs attention. Short cautious driving may be possible for some warnings if the vehicle otherwise behaves normally.
🟢 Green / 🔵 Blue
Usually InformationThese colours commonly confirm that headlights, cruise control, indicators, main beam or another normal function is active.
⚡ Flashing
Check ImmediatelyA flashing warning can mean something different from the same symbol displayed steadily. A flashing engine-management light, for example, can indicate an active severe misfire.
Stop somewhere safe if you have an oil-pressure warning, overheating, major brake-performance change, very heavy steering, severe engine misfire, smoke, burning smell, rapidly falling power or a dashboard instruction telling you to stop the vehicle.
An ABS light does not automatically mean the ABS pump has failed. A battery light does not automatically mean the battery is bad. An engine-management light does not automatically identify a sensor to replace. Use the warning together with symptoms and testing before buying parts.
Is It Safe to Drive?
Safety depends on the system and symptoms, not simply the colour of the lamp.
Browse Diagnostic Guides →Will It Fail the MOT?
UK MOT rules assess specific systems individually. There is no blanket rule that every warning light causes an MOT failure.
See UK MOT Rules →Not Sure What the Light Means?
Start with the warning colour, dashboard message and the vehicle's symptoms before narrowing the system.
Open Diagnostic App →What Do Dashboard Warning-Light Colours Mean?
Manufacturers use colour to help drivers judge priority, but there is no rule saying every red symbol means exactly the same thing or every amber symbol is safe to ignore. Treat colour as the first sorting step, then use the actual symbol, vehicle message and symptoms to decide what to do.
🟥 Red = Urgent
Often indicates a safety-critical fault, risk of mechanical damage or a condition that requires the driver to stop and investigate.
🟠 Amber = Attention
Usually means a monitored system has detected a problem or needs attention. Some amber faults allow cautious driving; others become urgent when symptoms appear.
🟢 Green = Active
Commonly confirms that a normal system such as exterior lighting, indicators or cruise control is switched on.
🔵 Blue = Active
Most commonly associated with main/high beam or another status indication rather than a mechanical failure.
⚪ White / Grey
Often used for information, driver-assistance status or a feature that is available but not currently active.
⚡ Flashing
Flashing can change the meaning or urgency completely. Always check the owner's handbook and accompanying dashboard message.
The DVSA inspection manual has separate requirements for systems such as ABS, SRS, power steering, TPMS and the engine malfunction indicator lamp. A warning's colour alone does not decide whether the vehicle passes or fails.
Red Dashboard Warning Lights: Stop, Check or Recover?
Red warning lights usually deserve the fastest response because they can relate to engine damage, braking safety, overheating, charging failure or another fault that may become serious quickly.
That does not mean every red symbol automatically fails an MOT or that every red light means the engine must be switched off instantly. The correct decision depends on the system involved, whether the warning is steady or flashing and what the car is doing at the same time.
Flashing Engine Light
❌ Stop / Diagnose UrgentlySevere misfire or combustion fault. Continuing to drive can overheat and damage the catalytic converter.
Flashing Engine Light →Oil Pressure
❌ Stop EngineLow oil pressure can remove the protective oil film from engine bearings and other moving parts.
Oil Pressure Warning →Coolant / Temperature
❌ Stop and Cool DownExcess engine temperature can quickly turn a small cooling-system fault into expensive engine damage.
Overheating Warning →Brake System
⚠️ / ❌ Depends on CauseIt may simply indicate the parking brake, but low fluid, hydraulic failure or changed pedal feel needs urgent attention.
Brake Warning →Battery / Charging
⚠️ Reach SafetyUsually means the vehicle is no longer charging correctly rather than simply that the battery itself is worn out.
Battery Warning →Airbag / SRS
⚠️ Drive Only if Otherwise SafeThe car may drive normally, but airbags or seat-belt pretensioners may not operate correctly in a collision.
Airbag / SRS Warning →If a red warning appears with smoke, steam, loss of braking, abnormal engine noise, heavy steering, severe misfire, burning smell or a dashboard message telling you to stop, move somewhere safe and switch off the vehicle rather than trying to complete the journey.
Flashing Engine Management Light
A flashing engine-management light is more urgent than a steady amber EML. It commonly means the ECU has detected a severe combustion or misfire problem capable of overheating the catalytic converter.
Meaning
Active Misfire / Combustion FaultSpark, injector, compression, fuelling or other combustion problems can leave unburned fuel entering the exhaust.
Safe to Drive?
❌ Usually NoIf the engine is shaking, losing power, smelling strongly of fuel or the warning continues flashing, stop and arrange diagnosis or recovery.
Quick Checks
Observe, Do Not GuessNote whether the engine is rough, which conditions trigger the warning and whether other lights appear. Avoid repeatedly restarting and revving a badly misfiring engine.
MOT Status
FAIL — Major Where MIL Inspection AppliesFor vehicles within the DVSA MIL inspection requirements, an engine malfunction indicator lamp that is inoperative or indicating a malfunction is a Major defect.
Typical UK Repair Cost
£40–£1,500+Diagnostic scanning may cost around £40–£100. Ignition coils or plugs can be relatively modest, while injector, catalyst or mechanical-engine faults can cost several hundred pounds or more.
A relatively modest ignition fault can become a much more expensive catalytic-converter repair if the engine is driven while unburned fuel is entering the exhaust.
Flashing Then Stops?
Intermittent flashing still matters because the fault may only occur under load, acceleration or specific engine conditions.
Flashing Engine Light Guide →Misfire Symptoms
Rough running, shaking, hesitation and loss of power can help narrow the underlying fault.
Engine Misfire Guide →Oil Pressure Warning Light
A red oil-can warning usually means the engine may not have enough oil pressure to lubricate itself correctly. It is not the same thing as an oil-service reminder.
Meaning
Lubrication Pressure ProblemPossible causes include low oil level, a faulty pressure sensor, blocked oil pickup, worn oil pump or internal engine wear.
Safe to Drive?
❌ NoContinuing to run the engine with genuinely low oil pressure can damage bearings, camshafts, turbochargers and other lubricated components very quickly.
Quick DIY Checks
Check Level When SafePark on level ground, switch off, allow the oil to settle and check the dipstick where fitted. If low, use the correct oil. Do not keep driving if the warning remains after the level is corrected.
MOT Status
Not a Blanket Warning-Light FAILThe red oil-pressure warning itself is not listed in the current car MOT manual as a universal standalone warning-lamp failure in the same way as an applicable engine MIL, ABS or SRS warning. Separate defects such as serious fluid leakage may still affect the MOT.
Typical UK Repair Cost
£10–£1,500+Correct oil may cost only £10–£40. A pressure switch can be around £60–£180 fitted, while oil-pump or internal-engine repairs can cost hundreds or thousands.
If the dipstick shows the correct level but the pressure warning remains illuminated, do not assume the sensor is faulty. Actual oil pressure should be tested before the engine is used further.
Use the Oil Leak Advisory Explained guide where the issue is visible oil leakage rather than oil pressure.
Coolant Temperature / Overheating Warning Light
A red coolant-temperature warning means the engine or cooling system is operating too hot. Some vehicles use a thermometer symbol, others display a red temperature message or tell the driver to stop the vehicle.
Meaning
Engine Temperature Too HighLow coolant, a leak, thermostat fault, failed water pump, radiator problem, fan fault or internal engine problem can all cause overheating.
Safe to Drive?
❌ NoContinued overheating can damage the cylinder head, head gasket, turbocharger and engine.
Quick DIY Checks
Only When Fully ColdAllow the vehicle to cool completely before checking coolant. Look underneath for leakage and check the expansion-tank level only when safe.
MOT Status
Not Automatically a Dashboard-Light FAILThe temperature warning itself is not treated as one universal dashboard-light MOT defect. However, a vehicle that is unsafe to test or has another testable defect can still fail or be refused testing as appropriate.
Typical UK Repair Cost
£80–£2,000+A hose may cost around £80–£200, thermostat £120–£350, water pump £250–£650, radiator £250–£700, while head-gasket or cylinder-head work can exceed £800–£2,000.
A hot cooling system is pressurised and can release boiling coolant or steam. Allow the engine to cool fully before opening the reservoir or radiator cap.
Coolant Warning Light
Separate low-level warnings from actual overheating and other cooling-system faults.
Coolant Warning Light Guide →Losing Coolant
Hidden leaks can evaporate, collect on an undertray or disappear internally.
Hidden Coolant Loss Guide →Repair Costs
Compare the likely cost once the cooling-system fault has been identified.
Coolant Leak Repair Cost →Brake System Warning Light
A red brake warning can mean different things depending on the car. It may simply show that the parking brake is applied, but it can also indicate low brake fluid, a hydraulic problem or another braking fault.
Meaning
Parking Brake / Fluid / Brake FaultThe same warning lamp can sometimes serve more than one braking function, so check the dashboard message and vehicle handbook.
Safe to Drive?
⚠️ / ❌ Depends on Pedal & BrakingIf the warning stays on with the parking brake released, braking feels different, the pedal is soft or fluid is low, stop and investigate rather than continuing normally.
Quick DIY Checks
Parking Brake & Visible Fluid LevelConfirm the parking brake is fully released. If the brake-fluid reservoir is transparent and safely visible, check whether the level is near the minimum mark without removing the cap.
MOT Status
Warning Lamp: Usually Minor; Serious Brake Faults Can FAILUnder the current DVSA manual, an illuminated or defective brake-fluid warning light is a Minor defect. Brake fluid significantly below minimum is Major, fluid not visible is Dangerous, and serious hydraulic or braking faults can separately cause Major or Dangerous failures.
Typical UK Repair Cost
£60–£1,000+Brake-fluid replacement may cost £60–£120, pads around £100–£220 per axle, while hydraulic, caliper, master-cylinder or ABS-related repairs can run into several hundred pounds.
The brake-fluid warning lamp itself can be Minor, while an ABS warning device showing a system malfunction is a Major defect. Always identify which symbol is actually illuminated.
Complete Brake Guide
Understand pads, discs, calipers, fluid, ABS and MOT braking defects.
Disc Brakes Explained →ABS Warning
If the illuminated symbol is ABS rather than the red brake lamp, follow the ABS diagnostic path.
ABS Warning Light Guide →Battery / Charging Warning Light
The red battery symbol usually means the charging system is not maintaining the vehicle's electrical supply correctly. It does not automatically mean the battery itself needs replacing.
Meaning
Charging System FaultPossible causes include an alternator fault, belt or tensioner problem, charging cable, poor connection, voltage regulator or battery-management issue.
Safe to Drive?
⚠️ Only to Reach SafetyOnce the battery's stored energy is exhausted, the engine or EV low-voltage systems may shut down and the vehicle may not restart.
Quick DIY Checks
Reduce Electrical LoadSwitch off heated screens, seat heaters and other unnecessary loads. Note dimming lights, steering changes or multiple warning lamps. Do not touch belts or charging components with the engine running.
MOT Status
Not an Automatic Standalone Warning-Light FAILThe battery/charging warning itself is not listed as one universal standalone MOT failure. The MOT does inspect relevant batteries, wiring and electrical equipment, and other faults can cause separate defects.
Typical UK Repair Cost
£90–£700+A battery may cost roughly £90–£300, while alternator replacement is often around £250–£700 or more. Wiring, belt and charging diagnosis can add further cost.
On some engines one auxiliary belt can drive the alternator and other components. If the charging warning appears with sudden heavy steering, overheating or unusual belt noise, stop rather than assuming it is only a battery fault.
Battery Warning Meaning
Understand the warning before replacing the battery.
Battery Warning Light Guide →Battery Keeps Going Flat
Test battery health, alternator output and parked electrical drain.
Battery Keeps Going Flat →Alternator Not Charging
Separate an alternator fault from battery, wiring and connection problems.
Alternator Charging Signs →Airbag / SRS Warning Light
The SRS warning relates to the vehicle's supplementary restraint system. Depending on the car, this can include airbags, crash sensors, seat-belt pretensioners, occupancy sensors, clocksprings and associated wiring.
Meaning
Restraint System MalfunctionA fault has been detected that may prevent some restraint components from operating correctly in a collision.
Safe to Drive?
⚠️ Vehicle May Drive NormallyThe fault may not affect steering or engine operation, but you should not assume all airbags and pretensioners remain available.
Quick DIY Checks
Visual Check OnlyLook for obvious objects disturbing wiring beneath the seats, but do not probe, unplug or test airbag connectors with ordinary electrical equipment.
MOT Status
FAIL — MajorThe current DVSA manual states that an SRS malfunction indicator lamp indicating a system malfunction is a Major defect. A lamp showing only that the passenger airbag has intentionally been switched off is not treated as that defect.
Typical UK Repair Cost
£50–£1,000+Diagnosis may be around £50–£120. Wiring or connector repairs can be relatively modest, while clocksprings, modules, sensors or airbag replacement can cost several hundred pounds or more.
Airbag and pretensioner circuits contain pyrotechnic components. Diagnosis should follow the manufacturer's procedure using appropriate equipment.
DVSA specifically states that a passenger airbag intentionally switched off is not itself a defect. The failure applies when the SRS malfunction indicator is actually indicating a system fault.
Read the Airbag Warning Light MOT Failure UK guide .
Amber Dashboard Warning Lights: Can You Keep Driving?
Amber or yellow warning lights normally mean a system needs attention, but they are not all equally urgent. Some allow cautious driving to a garage if the car feels completely normal; others become more serious when they appear with power loss, heavy steering, poor braking, overheating or additional warnings.
The safest approach is symptom-first: identify the symbol, read any dashboard message, note whether the light is steady or flashing and pay attention to how the vehicle is actually behaving.
Solid Engine Management Light
⚠️ Diagnose SoonThe ECU has detected a monitored fault. The car can sometimes drive normally even though the fault is MOT-relevant.
ABS
⚠️ Cautious Driving OnlyConventional braking may remain, but ABS intervention can be unavailable when you need it most.
TPMS
⚠️ Check Tyres FirstIt may simply mean a tyre is low, or the pressure-monitoring system itself may have malfunctioned.
DPF
⚠️ Act Before It EscalatesA diesel particulate filter may be becoming overloaded or a fault may be preventing regeneration.
EPS / Power Steering
⚠️ / ❌ Depends on SteeringIf steering suddenly becomes very heavy or inconsistent, stop rather than continuing normally.
AdBlue / SCR
⚠️ Refill or DiagnoseA low-level warning is different from an SCR-system malfunction, so read the accompanying message carefully.
Engine Management, ABS and TPMS Warning Lights
Solid Engine Management Light
A steady engine-management light means the ECU has detected a monitored engine or emissions-system fault. The car may feel completely normal, which is why this light is often ignored for too long.
Meaning
Engine / Emissions FaultPossible causes include oxygen sensors, misfires, air leaks, airflow sensors, catalyst efficiency, EGR, DPF, EVAP, injectors, boost faults or wiring problems.
Safe to Drive?
⚠️ SometimesShort cautious driving may be reasonable if the light is steady, the engine is smooth and there is no smoke, overheating, severe power loss or unusual noise.
Quick Checks
Scan Before Replacing PartsNote any symptoms and arrange a diagnostic scan. Do not assume a code naming a sensor proves that sensor itself has failed.
MOT Status
FAIL — Major Where MIL Inspection AppliesWhere the engine malfunction indicator lamp is within the vehicle's MOT inspection requirements, an inoperative MIL or one indicating a malfunction is a Major defect.
Typical UK Repair Cost
£40–£1,500+A scan may be around £40–£100, while sensor, ignition, injector, catalyst, DPF or wiring repairs can range from modest to very expensive.
Engine Light and MOT
See the full vehicle-date thresholds, tester checks and stored fault-code explanation.
Engine Management Light MOT Guide →Can You Keep Driving?
A steady warning with normal driving behaviour is different from a flashing light, misfire or limp mode.
Driving With EML On →ABS Warning Light
The ABS warning means the anti-lock braking system has detected a malfunction. Basic hydraulic braking may still operate, but the system designed to prevent wheel lock during heavy braking may not be available.
Meaning
Anti-Lock Braking FaultCommon causes include wheel-speed sensors, damaged sensor rings, wiring faults, wheel bearings, low voltage or ABS hydraulic / control-unit problems.
Safe to Drive?
⚠️ CautiouslyIf braking feels normal and no red brake warning is present, cautious travel for diagnosis may be possible. Stop if pedal feel, braking balance or stopping performance changes.
Quick Checks
Restart and InspectRestart once and note whether the light returns. Check for obvious tyre or wheel damage following recent repair or a hard impact, but proper fault-code diagnosis is normally required.
MOT Status
FAIL — MajorUnder the current DVSA manual, an ABS warning device showing a system malfunction is a Major defect. An ABS warning device that does not work is also Major.
Typical UK Repair Cost
£80–£1,200+A wheel-speed sensor may cost roughly £80–£220, while bearing, wiring, hydraulic-unit or ABS-module repairs can cost several hundred pounds or more.
Two braking warnings together can indicate more than the loss of anti-lock assistance. If braking performance or pedal feel is abnormal, stop and arrange inspection.
Continue with ABS Warning Light On — Is It Safe to Drive? for the detailed diagnostic pathway.
TPMS / Tyre Pressure Warning Light
A tyre-pressure warning can mean one or more tyres are below their expected pressure, but a flashing or persistent lamp can also indicate a fault within the tyre-pressure monitoring system itself.
Meaning
Low Pressure or TPMS FaultPressure can drop because of temperature change, a slow puncture, leaking valve, wheel damage or normal air loss. Sensor batteries and system faults can also trigger warnings.
Safe to Drive?
⚠️ Check Tyres FirstStop somewhere safe and inspect the tyres. Do not continue on a visibly flat, damaged or rapidly deflating tyre.
Quick DIY Checks
Measure All TyresCheck pressures using an accurate gauge and adjust them to the vehicle manufacturer's recommended cold pressures. Inspect for nails, sidewall damage and obvious leakage.
MOT Status
Depends on What the Warning MeansTPMS inspection applies to applicable M1 vehicles first used on or after 1 January 2012. A malfunctioning or obviously inoperative TPMS is a Major defect. An obviously underinflated tyre is a Minor defect. If the tester cannot tell whether the lamp means low pressure or a system malfunction, advisory information should be recorded.
Typical UK Repair Cost
£0–£250+Correcting pressure may cost nothing. Puncture repair may be around £20–£40, a tyre roughly £60–£250+, and a replacement TPMS sensor commonly around £50–£120 each.
Resetting a warning without checking the tyres can hide the real reason the system alerted you. Confirm tyre condition and pressure first.
DPF, Power-Steering and AdBlue Warning Lights
DPF Warning Light
A DPF warning means the diesel particulate filter or its monitoring system needs attention. The filter traps soot from diesel exhaust and periodically burns that soot away through regeneration.
Meaning
Soot Loading / Regeneration ProblemShort journeys, failed regeneration, pressure-sensor faults, temperature-sensor problems, EGR faults, injector problems or another engine fault can all contribute.
Safe to Drive?
⚠️ Often InitiallyIf the warning is the only symptom and the handbook permits it, a suitable drive may allow regeneration. Limp mode, multiple warnings or severe performance loss needs diagnosis instead.
Quick Checks
Read the MessageCheck the handbook for the vehicle-specific regeneration procedure. Do not repeatedly attempt forced regeneration where another engine fault is preventing the process.
MOT Status
Warning Alone Is Not the Whole TestThe MOT checks emissions-control equipment and diesel smoke. A manufacturer's emissions-control device that is missing, obviously modified or obviously defective is a Major defect. Evidence that a DPF has been tampered with can also fail the test.
Typical UK Repair Cost
£80–£2,000+Forced regeneration may cost around £80–£180, cleaning £150–£350, sensors £100–£300, while replacement filters can range from roughly £500 to £2,000 or more.
Injector problems, thermostat faults, EGR issues, failed sensors and repeated short journeys can all prevent regeneration or produce excessive soot. Find the cause before replacing the filter.
Continue with the DPF Warning Light Explained .
EPS / Power-Steering Warning Light
The steering warning means the power-assistance system has detected a fault. Depending on the vehicle, assistance may be electric, electro-hydraulic or conventional hydraulic.
Meaning
Steering Assistance FaultPossible causes include EPS motors, torque or position sensors, steering racks, wiring, low voltage, hydraulic faults or control-unit issues.
Safe to Drive?
⚠️ / ❌ Depends on SteeringIf steering is suddenly very heavy, jerky, inconsistent or hard to control, stop rather than attempting to continue the journey.
Quick Checks
Restart Once / Check Voltage CluesRestart once and note whether battery or charging warnings are also present. Low system voltage can trigger EPS faults on some vehicles.
MOT Status
FAIL — MajorThe current MOT manual classifies a power-steering system malfunction or inoperative power assistance as a Major defect. If steering is adversely affected, relevant defects can become Dangerous.
Typical UK Repair Cost
£50–£1,500+Diagnosis may be £50–£120, wiring or sensors £100–£400, while an EPS motor, column or steering rack can cost £500–£1,500 or more.
Electric power steering depends on a healthy low-voltage supply. A charging-system problem can sometimes trigger steering warnings alongside battery and other electrical faults.
AdBlue / SCR Warning Light
AdBlue is used by many diesel SCR systems to reduce nitrogen-oxide emissions. A dashboard message may simply mean the fluid level is low, or it may indicate an SCR-system malfunction.
Meaning
Low AdBlue or SCR FaultLevel warnings are different from faults involving pumps, injectors, heaters, NOx sensors, wiring or SCR-control components.
Safe to Drive?
⚠️ Usually InitiallyA simple low-level warning normally gives time to refill, but many vehicles eventually prevent restarting if the issue is not resolved.
Quick Checks
Refill Only if Level WarningUse the correct AdBlue and follow the manufacturer's minimum refill requirement. If the warning remains after a proper refill, diagnose the SCR system.
MOT Status
Depends on the Underlying Emissions FaultA low-level message alone is not one universal standalone MOT warning-lamp failure. However, emissions-control equipment that is missing, obviously modified or obviously defective can be a Major defect, and the vehicle must still meet its applicable emissions requirements.
Typical UK Repair Cost
£10–£1,500+AdBlue itself may cost only £10–£30. Sensors or injectors can cost £150–£500, while pumps, tanks and complex SCR repairs may reach £400–£1,500 or more.
“AdBlue low — 1,000 miles remaining” is a different problem from “AdBlue system fault — no restart in 500 miles”. The dashboard message can tell you whether the priority is simply topping up or diagnosing the emissions system.
Green and Blue Dashboard Lights: Usually Not Faults
Green and blue dashboard symbols usually tell you that a function is switched on or available rather than warning that a component has failed.
🔵 Main Beam
✅ NormalConfirms the main/high-beam headlamps are switched on.
🟢 Dipped / Exterior Lights
✅ NormalShows that the vehicle's exterior lighting is active.
🟢 Indicators
✅ NormalFlashing green arrows confirm direction indicators or hazards are operating.
🟢 Cruise Control
✅ Usually NormalCommonly confirms cruise control is enabled or actively holding speed.
🟢 Front Fog Lamps
✅ NormalConfirms the front fog lamps are switched on where fitted.
🟢 Start-Stop
✅ Usually NormalOften indicates that automatic engine stop-start is available or currently active.
🟢 EV READY
✅ NormalOn hybrids and EVs, READY often means the vehicle can move even though there is no engine sound.
🟢 Driver Assistance
✅ Usually ActiveLane-assistance, adaptive cruise and other driver aids often use green when actively functioning.
⚪ White / Grey Status
✅ InformationOften means a function is available, selected or waiting to activate.
A green or blue dashboard indication is not normally a fault in itself. However, the MOT still checks applicable equipment such as required lamps and the main-beam tell-tale where relevant.
An indicator arrow flashing unusually fast may suggest an exterior lamp fault, and a lighting tell-tale that does not behave normally can point towards a switch, lamp or electrical problem.
Flashing, Master Warning, Immobiliser and Hybrid / EV Lights
Modern dashboards can show symbols that do not fit neatly into the traditional red-and-amber categories. Hybrid and electric vehicles also add traction-battery, charging, regenerative-braking and high-voltage warnings.
⚡ Flashing Warning
Check ImmediatelyAlways find out why the light is flashing. A flashing EML can be urgent, while a flashing security LED after locking the car may be completely normal.
⚠️ Master Warning Triangle
Read the MessageA triangle with an exclamation mark often tells you to look at a separate dashboard message explaining the actual problem.
🔐 Immobiliser / Security
Depends on BehaviourA small security LED flashing after locking can be normal. A security warning while trying to start may indicate the key is not being recognised.
⚡ EV / Hybrid System Warning
⚠️ Diagnose PromptlyCan relate to traction battery control, inverter, electric motor, cooling, charging or hybrid-system management.
🔋 High-Voltage Battery Warning
⚠️ / ❌ Follow Vehicle MessageReduced power or a high-voltage fault message needs specialist diagnosis. If the vehicle tells you to stop safely, follow that instruction.
🔌 Charging Fault
⚠️ Check Before Next JourneyA charging warning may relate to the cable, charge point, onboard charger, battery temperature or high-voltage system.
♻️ Regenerative Braking Warning
⚠️ Braking Behaviour MattersSome EVs and hybrids temporarily reduce regenerative braking when the battery is full or cold. A genuine braking-system fault is different and needs diagnosis.
🔋 12V Battery Warning on EV
⚠️ Still ImportantEVs still depend on a 12V battery for control systems, contactors, lighting and vehicle startup. A 12V fault can immobilise an EV even when the traction battery is charged.
🌡 Battery Temperature Warning
⚠️ / ❌ Follow Manufacturer AdviceTraction batteries rely on temperature management. A serious overheating warning should not be treated like a normal range or charging message.
Hybrid and EV high-voltage systems can contain potentially lethal voltage even when the vehicle appears switched off. Do not remove traction-battery covers, unplug orange connectors or probe high-voltage circuits without the correct training and isolation procedure.
An electric or hybrid vehicle can be ready to move without engine noise. Always confirm the READY indication and vehicle state before working around or leaving the car.
There is no separate rule saying every hybrid or EV dashboard warning automatically fails. The tester applies the current defect criteria to the system involved, just as with petrol and diesel vehicles.
Which Dashboard Warning Lights Fail an MOT in the UK?
There is no single UK rule saying that every illuminated dashboard warning light automatically fails an MOT. The MOT tester applies the defect criteria for the specific system involved. That is why an ABS malfunction light can be a Major defect while a battery-charging warning is not automatically a standalone warning-lamp failure.
The current DVSA inspection manual for cars and passenger vehicles is updated to 1 June 2026. It uses the defect categories Minor, Major and Dangerous. Advisory information can also be recorded where something deserves attention but is not a testable defect at that level.
✅ PASS
No Relevant DefectA normal green or blue status lamp is not a fault simply because it is illuminated. The equipment itself must still meet any applicable MOT requirements.
⚠️ MINOR
MOT Still PassesA Minor defect does not cause an MOT failure, but it is recorded and should not be ignored. Some brake-fluid and tyre-pressure conditions fall into this category.
❌ MAJOR
MOT FAILMajor defects include several testable warning-system malfunctions such as ABS, SRS and applicable engine MIL faults.
❌ DANGEROUS
MOT FAILDangerous is used where a defect represents an immediate safety risk or seriously affects vehicle control or road safety.
Testers can record advisory information for developing conditions or matters that deserve monitoring. A vehicle can pass with advisory information, but repeated advisories can become test failures as wear or deterioration progresses.
| Dashboard warning / system | Typical MOT treatment | Result | Important detail |
|---|---|---|---|
| Applicable engine MIL / EML showing malfunction | Major defect | ❌ FAIL | Only where the vehicle falls within the applicable engine-MIL inspection requirements. |
| Applicable engine MIL inoperative | Major defect | ❌ FAIL | Disabling or hiding a required MIL does not solve the problem. |
| ABS warning device showing system malfunction | Major defect | ❌ FAIL | ABS warning device not working is also Major. |
| SRS / airbag MIL showing system malfunction | Major defect | ❌ FAIL | A passenger-airbag-disabled indication is not itself this defect. |
| EPS / power-steering system malfunction | Major defect | ❌ FAIL | Steering defects can become Dangerous if vehicle control is adversely affected. |
| TPMS malfunction on applicable vehicle | Major defect | ❌ FAIL | Applies to relevant M1 vehicles first used on or after 1 January 2012. |
| Tyre obviously underinflated | Minor defect | ⚠️ PASS with defect | A damaged, illegal or unsafe tyre may separately create a more serious failure. |
| Brake-fluid warning light illuminated or defective | Minor defect | ⚠️ PASS with defect | Actual fluid level and braking-system condition are assessed separately and can produce Major or Dangerous defects. |
| DPF / emissions equipment missing or obviously defective | Major defect | ❌ FAIL | The warning lamp alone is not the complete emissions inspection. |
| Battery / charging warning light | Not a universal standalone warning-lamp defect | Depends | Battery, wiring and other electrical defects can still be testable separately. |
| Oil-pressure warning | Not a universal standalone warning-lamp defect | Depends | The warning may still indicate an urgent mechanical problem even where the lamp itself is not the MOT failure. |
| Coolant-temperature warning | Not a universal standalone warning-lamp defect | Depends | Severe overheating can make the vehicle unsafe regardless of the warning-lamp MOT classification. |
| Green / blue normal status indicator | Normally not a fault | ✅ Usually PASS | Required lamps, switches and tell-tales must still operate correctly where the MOT checks them. |
The visible engine MIL inspection and the exhaust-emissions test are separate. A vehicle can meet the measured emissions limits yet still fail because an applicable MIL is indicating a malfunction.
DVSA specifically notes in the SRS inspection that warning messages displayed on the dashboard are not defects in their own right, although they can help a tester establish why a warning lamp is illuminated. The actual testable system and defect wording matter.
Engine Light MOT Rules
See vehicle dates, MIL self-check behaviour and Major-defect logic in detail.
Engine Light MOT Guide →Airbag Warning MOT Rules
Understand the distinction between an SRS malfunction and an intentionally disabled passenger airbag.
Airbag Warning MOT Guide →Common MOT Failures
Warning lights are only one part of the test. Tyres, brakes, suspension, lamps and emissions also account for failures.
Common MOT Failure Reasons →What Should You Check When a Dashboard Warning Light Appears?
The quickest way to waste money is to replace the component that seems to match the dashboard icon. A warning lamp identifies a system or condition that needs attention; diagnosis establishes the actual cause.
Use the warning light together with what the car is doing. A battery warning plus heavy steering tells you more than the battery symbol alone. An EML plus severe shaking tells you more than a stored fault code alone.
1. Identify the Symbol
Confirm whether the lamp represents the engine, ABS, tyres, battery, oil, coolant, SRS, steering or another system.
2. Check the Colour
Red generally means greater urgency, amber normally requires diagnosis and green or blue often indicates normal operation.
3. Steady or Flashing?
Flashing can change the meaning significantly. A flashing engine lamp, for example, can indicate an active severe misfire.
4. Read the Dashboard Message
Modern vehicles often explain whether the issue is low fluid, reduced power, a system malfunction or an instruction to stop.
5. Check What Changed
Did the steering become heavy? Did the engine start shaking? Did braking change? Did temperature rise? Those symptoms set the urgency.
6. Decide Whether to Stop
Oil-pressure loss, overheating, severe brake faults, dangerous steering changes and strong misfires are reasons to prioritise safety over completing the journey.
7. Make Only Safe Basic Checks
Check tyre pressures, cold fluid levels and obvious loose connections where appropriate. Never open a hot cooling system or work on live high-voltage components.
8. Scan Electronic Systems
Engine, ABS, SRS, steering and many hybrid/EV faults require diagnostic trouble codes and system data before the cause can be narrowed down.
9. Record Codes Before Clearing
Save current, pending and stored codes plus freeze-frame information where available before deleting anything.
10. Test the System
Electrical supply, wiring, live data, pressure, temperature, mechanical condition or another targeted test may be required.
11. Repair the Proven Cause
Replace a sensor, battery, pump, module or mechanical component only after testing supports the repair.
12. Confirm the Warning Stays Off
Road test where appropriate, rescan and confirm that the system has returned to normal operation before assuming the repair is complete.
Erasing a code does not repair a failing ABS sensor, misfire, charging fault, airbag circuit, DPF problem or steering defect. If the underlying fault remains, the warning can return.
Low charging voltage, for example, can produce battery, steering, ABS and stability warnings together. Diagnose what all the symptoms have in common before replacing several unrelated control units.
Diagnose by Symptom
Work from what the vehicle is actually doing, not just the dashboard icon.
Diagnostics Hub →Guided Diagnosis
Compare warning lights with starting, power, braking, steering, cooling and electrical symptoms.
Open Diagnostic App →Browse Warning Lights
Move from this pillar into the specialist warning-light guides.
Warning Lights Hub →How Much Does It Cost to Fix a Dashboard Warning Light?
There is no fixed price for “turning off a warning light”. The cost depends on the underlying fault. A low tyre may cost nothing to correct, while an ABS hydraulic unit, steering rack, DPF, catalyst or high-voltage system fault can cost hundreds or thousands of pounds.
These figures are realistic UK planning ranges rather than fixed quotations. Vehicle model, labour rate, diagnostic time, component quality and access can change the final bill considerably.
Diagnostic Scan
£40–£100+Reading codes identifies which system needs investigation, but proper diagnosis may require further tests.
Battery Replacement
£90–£300+AGM, EFB and vehicle-specific battery-management requirements can increase replacement cost.
Battery Diagnosis →Alternator
£250–£700+Test charging output, wiring and belt drive before condemning the alternator.
Alternator Cost Guide →ABS Sensor
£80–£220+An ABS sensor code can also result from damaged wiring, reluctor rings or wheel-bearing problems.
ABS Module / Hydraulic Unit
£400–£1,200+Confirm sensors, wiring, supply voltage and hydraulic faults before replacing the control unit.
Airbag / SRS Diagnosis
£50–£120+Wiring, seat sensors, pretensioners, clocksprings and modules can all trigger an SRS warning.
Airbag / SRS Repair
£80–£1,000+Connector or wiring faults may be modest, while modules, clocksprings or airbag components can cost significantly more.
TPMS Sensor
£50–£120 EachSensor batteries eventually fail and some replacements require programming or relearning.
DPF Cleaning / Regeneration
£80–£350+Regeneration or cleaning is not a permanent fix if another engine fault continues creating excessive soot.
DPF Replacement
£500–£2,000+Vehicle type and whether genuine or aftermarket parts are used can change the price considerably.
EPS / Steering Repair
£100–£1,500+The cause can range from wiring or voltage faults to an EPS motor, steering column or complete rack.
Cooling-System Repair
£80–£2,000+A hose or thermostat is very different from water-pump, radiator or head-gasket repair.
Coolant Repair Cost Guide →| Warning family | Typical starting cost | High-cost possibility | Best first step |
|---|---|---|---|
| Engine management | £40–£100 diagnosis | £1,500+ catalyst / engine fault | Scan, record data, test system |
| Battery / charging | £60–£120 testing | £700+ alternator / wiring | Battery and charging test |
| ABS | £80–£220 sensor | £1,200+ hydraulic/module repair | Scan ABS system and inspect wheel data |
| SRS / airbag | £50–£120 diagnosis | £1,000+ component repair | Specialist diagnostic scan |
| TPMS | £0 pressure correction | £120+ per sensor / tyre extra | Inspect tyre and measure pressure |
| DPF | £80–£180 regeneration | £2,000+ replacement | Check loading and regeneration cause |
| Power steering | £50–£120 diagnosis | £1,500+ rack / EPS component | Check steering behaviour and fault codes |
| Cooling / overheating | £80–£200 minor leak | £2,000+ engine repair | Stop overheating and diagnose leak |
Spending money confirming the cause can prevent an unnecessary battery, ABS module, oxygen sensor, DPF, steering rack or other expensive component being fitted.
What Should You Do About Dashboard Warning Lights Before an MOT?
Do not wait until the morning of the MOT to investigate a warning light. Some faults need diagnosis, parts and a road test before you can be confident that the warning will stay off.
- 1 Switch the ignition on and observe the self-check. Note which warning lamps illuminate before the engine starts.
- 2 Start the vehicle. Check which lights go out and which remain illuminated.
- 3 Identify every remaining warning. Do not assume several lamps are one fault.
- 4 Read dashboard messages. Record the wording before switching the car off.
- 5 Check tyre pressures. Correct genuine low-pressure warnings before resetting TPMS.
- 6 Check safe fluid levels. Inspect oil, coolant and brake fluid only using the correct procedure and never open a hot cooling system.
- 7 Scan testable electronic systems. Engine, ABS, SRS and steering faults normally need fault-code diagnosis rather than guesswork.
- 8 Repair the actual cause. Do not remove bulbs, mask warnings or clear codes only to obtain a temporary clean dashboard.
- 9 Road test where safe. Confirm the repaired system behaves normally under the conditions that previously triggered the warning.
- 10 Rescan before test day. Check whether current or pending faults have returned.
- 11 Check exterior lamps too. A clean dashboard does not mean the vehicle's headlights, indicators, brake lights and rear lights all meet MOT standards.
- 12 Leave time before the MOT. Investigate warnings several days beforehand where possible so parts and further diagnosis can be completed properly.
Several systems require the warning device itself to operate correctly. For example, an ABS warning device not working is a Major defect. Hiding the lamp can therefore create another failure rather than solve the original fault.
If an ABS, SRS, EPS or applicable engine MIL remains illuminated, diagnose it before presenting the vehicle. If the warning relates to oil pressure, overheating, braking performance or unsafe steering, deal with the safety problem before worrying about the MOT itself.
Full MOT Preparation
Check tyres, lamps, brakes, visibility and other common failure areas as well as dashboard warnings.
Prepare for Your MOT →Warning Lights Hub
Continue into the specialist guides for the individual symbol showing on your dashboard.
Browse Warning Lights →Diagnostic App
Match the warning light with the vehicle's actual symptoms before replacing parts.
Open Diagnostic App →Dashboard Warning Lights Cheat Sheet
Use this as a fast first check when a warning appears. The colour helps you judge urgency, but the final decision should always include the actual symbol, whether it is flashing, any dashboard message and the way the vehicle is behaving.
🟥 RED
STOP / CHECK NOWOil pressure, overheating and serious braking warnings can lead to rapid damage or loss of safety if ignored.
🟠 AMBER
DIAGNOSE SOONSome amber warnings allow short cautious driving when the car feels completely normal, but they should not be left unresolved.
🟢 GREEN / 🔵 BLUE
USUALLY NORMALCommonly confirms that lights, cruise control, indicators or another normal vehicle function is operating.
⚡ FLASHING
CHECK THE MEANINGFlashing often changes the meaning. A flashing EML, for example, can indicate an active severe misfire rather than an ordinary stored engine fault.
| Warning | Safe to drive? | MOT position | First action |
|---|---|---|---|
| Flashing engine light | ❌ Usually no | Major where MIL test applies | Stop severe misfire and diagnose |
| Oil pressure | ❌ No | Not universal lamp failure | Stop engine and check oil safely |
| Overheating | ❌ No | Not universal lamp failure | Stop and allow engine to cool |
| Red brake warning | ⚠️ / ❌ | Depends on actual brake defect | Check parking brake and braking behaviour |
| Battery / charging | ⚠️ Reach safety | Not universal lamp failure | Reduce electrical load and diagnose charging |
| Airbag / SRS | ⚠️ | ❌ Major when malfunction indicated | Arrange SRS diagnosis |
| Solid engine light | ⚠️ Sometimes | ❌ Major where MIL test applies | Scan and diagnose |
| ABS | ⚠️ If normal braking remains | ❌ Major | Scan ABS system |
| TPMS | ⚠️ Check tyre first | Major if system malfunction on applicable vehicle | Measure pressures and inspect tyre |
| DPF | ⚠️ Often initially | Depends on emissions/control defect | Check regeneration conditions and faults |
| EPS | ⚠️ / ❌ | ❌ Major for malfunction | Stop if steering becomes unsafe |
| Green / blue status lamp | ✅ Usually yes | Usually not a fault | Confirm normal system operation |
A warning lamp does not need to be an automatic MOT failure to be dangerous. Oil-pressure loss, overheating, serious braking changes and unsafe steering require attention because of the risk to the vehicle or occupants, not simply because of an annual test.
Related Dashboard Warning Light & Diagnostic Guides
This page is the broad warning-light pillar. Once you know which system is involved, move into the specialist guide below for deeper diagnosis, MOT rules and repair decisions.
Engine Management Light
Understand the EML, common engine and emissions causes and what the warning means before replacing sensors.
Engine Management Light Guide →Engine Light and MOT
See the applicable petrol and diesel dates, tester checks and Major-defect rules.
Will EML Fail MOT? →Flashing Engine Light
Diagnose intermittent flashing, misfires and catalyst-damage risks.
Flashing Engine Light Guide →Engine Misfire
Rough running, shaking, hesitation and ignition or combustion faults explained.
Engine Misfire Guide →ABS Warning Light
Learn why ABS faults appear and when normal braking may still remain.
ABS Warning Light Guide →Airbag Warning Light
SRS faults, crash protection and exact MOT failure logic.
Airbag Warning MOT Guide →Battery Warning Light
Separate battery failure from alternator, belt, wiring and charging faults.
Battery Warning Light Guide →Battery Keeps Going Flat
Diagnose battery health, charging and parked electrical drain.
Battery Keeps Going Flat →Alternator Not Charging
Charging voltage, alternator output and related electrical symptoms explained.
Alternator Charging Guide →DPF Warning Light
Soot loading, regeneration, pressure sensors and diesel emissions faults.
DPF Warning Light Guide →Coolant Warning Light
Low coolant, temperature warnings and cooling-system problems explained.
Coolant Warning Light Guide →Hidden Coolant Loss
Diagnose coolant loss when there is no obvious puddle under the car.
Losing Coolant With No Leak →Coolant Repair Costs
Compare likely repair costs once the cooling-system fault is confirmed.
Coolant Leak Repair Cost →Disc Brakes Explained
Understand brake warning symptoms, ABS, fluid, pads, discs and braking-system faults.
Disc Brakes Guide →Warning Lights Hub
Browse Motor Vehicle Expert's dedicated dashboard warning-light guides.
Warning Lights Hub →Diagnostics Hub
Diagnose the vehicle from its real symptoms rather than a warning light alone.
Diagnostics Hub →Diagnostic App
Work through warning lights, starting faults, power loss, steering, brakes and other symptoms step by step.
Open Diagnostic App →Prepare for Your MOT
Check warning lamps together with tyres, brakes, lights, visibility and other common failure points.
MOT Preparation Guide →This pillar explains what the warning colours and major symbols mean. The specialist guides go deeper into fault patterns, MOT requirements, testing and repair decisions for each individual system.
Dashboard Warning Light FAQs
These are the most common questions UK drivers ask about dashboard warning lights, driving safety, MOT failures, fault codes and what to do before test day.
Can I pass an MOT with a dashboard warning light on?
Sometimes. There is no blanket rule that every warning light causes an MOT failure. The result depends on the system involved. An applicable engine MIL, ABS malfunction warning, SRS malfunction warning, EPS fault or applicable TPMS malfunction can cause a Major defect, while many normal green and blue status lights are not faults.
What does a red dashboard warning light mean?
Red usually means urgent attention is required. Oil-pressure, overheating and serious brake warnings should be treated particularly seriously because continued driving can cause damage or create a safety risk.
Can I drive with an amber warning light?
Sometimes, if the warning is steady and the vehicle feels completely normal. Stop instead if the warning is accompanied by heavy steering, braking problems, severe power loss, overheating, smoke, misfire or another serious symptom.
What does a flashing engine management light mean?
A flashing engine-management light commonly indicates a severe combustion or misfire fault. Continued driving can send unburned fuel into the exhaust and damage the catalytic converter, so the vehicle should be stopped and diagnosed promptly.
Will a solid engine management light fail an MOT?
Yes where the vehicle is within the DVSA engine-MIL inspection requirements. An applicable MIL that is inoperative or indicating a malfunction is classed as a Major defect.
Will an ABS warning light fail an MOT?
Yes. An ABS warning device showing a system malfunction is a Major defect. An ABS warning device that does not operate correctly is also a Major defect.
Will an airbag warning light fail an MOT?
Yes when the SRS malfunction indicator is showing a system malfunction. That is a Major defect. A lamp simply indicating that the passenger airbag has intentionally been switched off is not the same defect.
Will a tyre-pressure warning light fail an MOT?
It depends on what the lamp is indicating. On applicable M1 vehicles first used on or after 1 January 2012, a malfunctioning or obviously inoperative TPMS is a Major defect. A tyre that is simply obviously underinflated is classed as a Minor defect.
Does a battery warning light mean the battery is bad?
Not necessarily. The battery symbol normally indicates a charging problem. Possible causes include the alternator, drive belt, charging cable, voltage regulator, poor electrical connections or the battery itself.
Can I drive with the battery warning light on?
Only cautiously to reach a safe place if the vehicle remains normal. If the charging system has failed, the vehicle may stop once the battery is discharged. Stop sooner if heavy steering, overheating or multiple electrical warnings appear.
What should I do when the oil-pressure warning comes on?
Stop the engine as soon as safely possible. Once the vehicle is level and the oil has settled, check the oil level where a dipstick is fitted. Do not continue running the engine if the warning remains on after the oil level is confirmed correct.
Can I drive with the coolant-temperature warning light on?
No. Stop somewhere safe and allow the engine to cool fully. Continued overheating can damage the cylinder head, head gasket and other engine components. Never remove a hot pressurised coolant cap.
Does a DPF warning light automatically fail an MOT?
The DPF warning lamp by itself is not the complete MOT test. However, emissions-control equipment that is missing, obviously modified or obviously defective is a Major defect, and evidence of DPF tampering can also cause failure.
Does an EPS or power-steering warning light fail an MOT?
A malfunctioning power-steering system or inoperative power assistance can be a Major defect. Steering defects can become Dangerous where vehicle control is adversely affected.
Are green and blue dashboard lights faults?
Usually not. Green and blue symbols commonly confirm that a normal function such as exterior lighting, main beam, indicators or cruise control is active. The underlying equipment must still work correctly where the MOT tests it.
Should all warning lights come on when I switch the ignition on?
Many warning lamps illuminate briefly as part of a self-check and then go out when the system is confirmed healthy. The exact sequence varies by vehicle. Some testable systems can fail the MOT if their required warning device is inoperative.
Can I clear a warning light before an MOT?
Clear diagnostic codes only after the underlying fault has been diagnosed and repaired. Erasing a code does not fix a misfire, ABS sensor, airbag circuit, charging fault, DPF problem or steering malfunction, and the warning can return.
How much does it cost to fix a dashboard warning light?
The cost depends entirely on the cause. Diagnosis may start around £40 to £100, while relatively simple sensor or wiring repairs may cost a few hundred pounds. ABS modules, DPFs, steering racks, catalysts and complex hybrid or EV faults can cost £1,000 or more.