Motor Vehicle Expert
Diagnostics Hub

Car Diagnostics, Warning Lights and Fault-Finding Guides

Use this diagnostics hub to find practical UK guides for warning lights, starting problems, battery and charging faults, overheating, coolant loss, smoke, smells, vibration, jerking, braking symptoms, steering issues and common vehicle problems.

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✓ Warning light diagnosis ✓ Symptom-based fault finding ✓ MOT-aware guidance ✓ UK-focused repair advice
Explore our specialist hubs:

Browse our specialist hubs covering Cooling System Guides, MOT Failure Guides and Used Car Buying Guides for deeper fault-finding and ownership advice.

Professional diagnostic approach

Good diagnosis starts with the first symptom that appeared: warning light, overheating, vibration, smoke, smell, poor starting or loss of power. Following the symptom first helps avoid unnecessary parts replacement.

Starting

Car won't start?

Battery, starter, alternator or immobiliser issues.

Find causes →
Cooling

Overheating?

Coolant loss, thermostat, fan or radiator problems.

Check cooling faults →
Power loss

Car feels weak?

Misfire, turbo, DPF or fuel delivery issues.

Check running faults →
Warning lights

Dashboard warning?

Engine, ABS, oil, battery or steering alerts.

Open warning lights →
Free diagnostic app Warning lights Overheating and coolant Cooling System Hub Starting and charging Jerking and power loss Vibration and steering Smells and smoke Heater, AC and electrical MOT Failure Hub Used Car Buying Hub More guides
Free diagnostic tool

Use The Motor Vehicle Expert Diagnostic App

Before browsing individual guides, you can use the free diagnostic app page to check dashboard warning lights, vehicle symptoms, OBD fault codes, possible causes, safe-to-drive guidance and MOT implications.

Warning lights

Engine, battery, oil, coolant, ABS, airbag, brakes and tyre pressure warnings.

Vehicle symptoms

Overheating, misfire, no start, smoke, clicking noise, rough idle and power loss.

OBD codes

Common diagnostic codes such as P0300, P0171, P0420 and P0101.

MOT-aware advice

Understand whether a warning light or fault could affect an MOT test.

Open Diagnostic App Page Warning Light Guide
Find by symptom

Start with the symptom you notice first

Most car faults are easier to narrow down when you start with the real-world symptom: warning light, noise, smell, smoke, vibration, overheating, coolant loss or poor running.

Warning

Dashboard warning light on?

Engine, oil, battery, ABS, airbag, coolant, brake, EPC, TPMS and traction control warnings.

Browse warning lights →
Cooling

Overheating or losing coolant?

Coolant loss, bubbling, fan faults, thermostat problems, head gasket signs and radiator issues.

Browse cooling guides →
Running

Jerking, hesitation or power loss?

Misfires, rough idle, acceleration faults, sluggish running, bucking, stuttering and gear-change jolts.

Browse running faults →
Vibration

Shaking or vibration?

Idle vibration, steering shake, high-speed vibration, braking judder and pulling to one side.

Browse vibration guides →
Smell

Burning, petrol or coolant smell?

Burning oil, rubber, clutch, coolant, petrol, exhaust, rotten egg and hot smells after driving.

Browse smell guides →
Start

Car will not start?

Cranking, clicking, flat battery, alternator, starter motor and charging faults.

Browse starting guides →
Warning lights

Dashboard warning light guides

Start here if a dashboard warning light has appeared, keeps returning or has changed how the car drives. Red lights, oil pressure warnings, brake warnings and overheating warnings should be treated seriously.

App

Diagnostic App Warning Light Lookup

Use the app page to check dashboard warning lights, severity, safe-to-drive guidance and MOT implications.

Use warning light checker →
All lights

Car Warning Lights Meaning UK

A broader guide to common dashboard symbols and what to check first.

Read warning light guide →
Engine

Engine Management Light Explained

What the engine management light can mean, when it is urgent and what to do next.

Read engine light guide →

Can You Drive With Engine Management Light On?

Steady vs flashing warning light, safe driving advice and when to stop.

Check safe driving advice →

Will Engine Management Light Fail MOT?

When engine warning lights can affect MOT results and what to do before a test.

Read MOT warning guide →

Battery Warning Light Meaning

Charging system faults, alternator issues, belts and poor connections.

See charging faults →

Battery Light On After New Battery

Why a battery warning light can stay on after a new battery is fitted.

Read diagnosis guide →

Brake Warning Light On While Driving

Low brake fluid, brake faults, handbrake issues and when to stop driving.

Read brake warning guide →

ABS Warning Light On: Is It Safe to Drive?

ABS warning causes, wheel speed sensors, braking safety and MOT risk.

Open ABS guide →

Airbag Warning Light MOT Failure UK

Whether an airbag warning light can fail an MOT and what drivers should do.

Read airbag guide →

DPF Warning Light Explained

Diesel particulate filter warnings, regeneration and limp mode.

Open DPF guide →

EPC Warning Light Meaning UK

Common EPC light causes and whether it is safe to keep driving.

Read EPC guide →

Power Steering Warning Light Meaning

Power steering warning causes and when it may be unsafe to drive.

Check steering warning →

Tyre Pressure Warning Light Reset UK

Why the TPMS light comes on, what to check and how reset systems work.

Read TPMS guide →

Traction Control Light On But Car Drives Fine

Why traction control warnings can appear even when the car seems normal.

Read traction guide →
Cooling system and overheating

Coolant loss, overheating, radiator, fan and head gasket guides

Use these pages when the car runs hot, loses coolant, shows a coolant warning, blows cold air from the heater, bubbles in the expansion tank or produces white smoke.

App

Check Overheating In The App

Use the diagnostic app page to check overheating symptoms, possible causes and safe-to-drive advice.

Open diagnostic app →
Cooling hub

Cooling System Guides UK

Complete cooling hub covering coolant leaks, overheating, radiator fans, thermostats, water pumps, white smoke and repair costs.

Open cooling hub →
Urgent

Car Overheating: What To Do

Immediate steps, when to stop driving and how to avoid further engine damage.

What to do now →
Coolant

Car Losing Coolant But No Leak

Hidden coolant loss, internal leaks, pressure issues and head gasket clues.

Read coolant loss guide →

Coolant Bubbling In Expansion Tank

Airlocks, boiling coolant, pressure build-up and head gasket warning signs.

Read bubbling guide →

White Smoke From Exhaust Coolant

When white smoke may point to coolant entering the combustion chamber.

Read white smoke guide →

Car Overheats With Air Conditioning On

Cooling fan, condenser airflow and radiator load problems with AC on.

AC overheating guide →

Thermostat Stuck Open or Closed

Slow warm-up, overheating, heater issues and temperature gauge clues.

Thermostat symptoms →

Water Pump Failure Symptoms

Poor coolant circulation, leaks, overheating, whining noises and heater issues.

Water pump symptoms →

Radiator Blocked Symptoms

Blocked radiator signs, poor coolant flow, overheating and hot/cold radiator areas.

Blocked radiator guide →

Car Temperature Gauge Going Up and Down

Fluctuating gauge readings, thermostat, coolant, fan and sensor causes.

Temperature gauge guide →

Car Heater Blows Cold Then Hot

Heater temperature changes caused by coolant, airlocks, thermostat or flow issues.

Heater temperature guide →

Coolant Leak Repair Cost UK

Common coolant leak sources, repair costs and warning signs.

Coolant leak costs →
Starting, battery and charging

Car won’t start, weak battery and charging faults

Use these guides when the car clicks, cranks, will not start, keeps going flat or shows battery and charging symptoms.

App

Check No-Start Faults In The App

Use the app page to check car won’t start, clicking noise, battery warning and charging symptoms.

Open diagnostic app →
Hub

Car Won’t Start Diagnosis Guide

A central guide to battery, starter, fuel, ignition, immobiliser and charging causes.

Open no-start guide →

Car Won’t Start But Battery Seems Fine

Starter motor, immobiliser, ignition and fuel faults.

Read guide →

Starter Motor Clicking But Not Starting

Single click, rapid clicking, battery faults and starter motor problems.

Starter clicking guide →

How To Check Car Battery Health

Weak battery symptoms, simple checks and charging system warning signs.

Battery health guide →

Car Battery Keeps Going Flat

Old battery, alternator faults, short trips and overnight drain.

Flat battery guide →

Starter Motor Replacement Cost UK

Starter motor symptoms, common UK costs and why diagnosis matters.

Starter motor costs →
Running, idle and acceleration faults

Misfire, rough idle, hesitation, jerking and power loss

Use these guides when the car feels rough, weak, jerky, hesitant, sluggish or uneven under acceleration.

App

Check Symptoms In The App

Use the diagnostic app page for misfire, loss of power, rough idle and power loss guidance.

Use symptom checker →
Hub

Car Jerks When Accelerating

Main hub for acceleration jerking, bucking, stuttering, hesitation and juddering.

Open jerking guide →
Misfire

Engine Misfire Symptoms and Causes

Rough idle, shaking, hesitation, warning lights and power loss.

Misfire diagnosis →

Car Losing Power When Accelerating

Fuel, turbo, DPF, misfire and limp mode causes.

Power loss guide →

Car Feels Slow To Accelerate

Sluggish acceleration, fuel issues, sensors, clutch slip and servicing faults.

Sluggish car guide →

Car Loses Power Uphill

Uphill power loss, clutch slip, turbo faults, fuel issues and DPF problems.

Uphill power loss →

Car Hesitates When Accelerating

Flat spots, hesitation, fuel faults, ignition issues and sensors.

Hesitation guide →

Car Stutters When Accelerating

Stuttering, misfires, fuel problems and poor acceleration causes.

Stuttering guide →

Car Revs But Won’t Accelerate

Clutch slip, gearbox faults and drivetrain causes of poor drive.

Revs but no drive →
Brakes, steering, tyres and vibration

Braking, vibration, pulling and wheel symptoms

These guides cover symptoms you may feel through the steering wheel, brake pedal, suspension, wheels or tyres.

Hub

Car Shaking and Vibration Diagnosis

Main hub for vibration at idle, speed, braking, acceleration and steering wheel shake.

Open vibration hub →
Steering

Why Does My Steering Wheel Shake?

Wheel balancing, tyre damage, brake issues and suspension problems.

Steering shake guide →

Car Shakes At High Speed

High-speed vibration from wheels, tyres, balancing and suspension.

High-speed shake →

Car Pulling To One Side Causes

Tyres, alignment, brakes and suspension causes of pulling or drifting.

Pulling guide →

Brake Warning Signs

Grinding, squealing, soft pedal feel and unstable braking symptoms.

Brake symptoms →

Car Clicking Noise When Turning

Clicking while turning, CV joints, suspension and steering causes.

Clicking noise guide →

Wheel Bearing Noise When Speeding Up

How bearing noise changes with speed and when repair is needed.

Wheel bearing noise →
Smells, smoke and engine clues

Burning, coolant, petrol, exhaust smells and smoke

Smells and smoke can give useful clues about leaks, overheating, clutch wear, exhaust faults, fuel vapours and electrical problems.

Hub

Car Smells Guide

Learn what burning oil, coolant, petrol, exhaust and rotten egg smells can mean.

Open smell guide →
Smoke

Exhaust Smoke Colour Guide

White, blue, black and grey exhaust smoke explained.

Smoke colour guide →
Coolant

White Smoke From Exhaust Coolant

When white smoke may be linked to coolant loss or head gasket symptoms.

White smoke guide →

Car Smells Like Coolant

Sweet coolant smells, leaks, heater matrix and overheating clues.

Coolant smell guide →

Car Smells Hot After Driving

Hot smells after driving, brakes, oil, coolant and engine heat.

Hot smell guide →

Car Smells Like Burning Oil

Oil leaks, hot engine parts and urgent warning signs.

Burning oil smell →
Heater, AC and electrical

Cabin, comfort and electrical faults

Useful guides for heating, cooling, locks, windows, radio and key-related problems.

Car AC Not Blowing Cold Air

Air conditioning not cooling, refrigerant, compressor and fan faults.

AC diagnosis guide →

Car Heater Not Blowing Hot Air

Heater problems, coolant, thermostat and blower-related faults.

Heater fault guide →

Car Key Fob Not Working

Key battery, remote locking, programming and receiver faults.

Key fob guide →
Common symptom categories

What kind of problem are you dealing with?

  • 1Dashboard warning lights and fault messages.
  • 2Starting problems, battery faults and charging issues.
  • 3Coolant loss, overheating, smoke or engine temperature changes.
  • 4Rough running, misfire, hesitation, jerking or loss of power.
  • 5Vibration, shaking, pulling, braking problems or unusual smells.
Good diagnostic habits

How to approach a fault sensibly

1. Notice the pattern

When does it happen: cold, hot, idle, braking, accelerating, uphill, traffic or motorway speed?

2. Avoid guessing

Do not replace parts at random just because they are commonly blamed online.

3. Judge urgency

Coolant, oil, brake, steering, smoke and overheating faults can become unsafe quickly.

4. Confirm the cause

Use proper checks, fault-code reading and inspection before spending money.

Motor Vehicle Expert publishes practical UK-focused vehicle diagnostics, maintenance, MOT and used car guidance based on common driver symptoms, dashboard warning lights and real-world repair questions.