Service, Repairs & MOT

Car diagnostic

Book an RAC Mobile Mechanic and we’ll come to you at home or work.

  • 12-months parts guarantee
  • Honest pricing
  • Exceptional customer service

Trustpilot rating for all RAC Mobile Mechanics.

Why choose the RAC for a car diagnostic?

At the RAC, we've got over 125 years' experience helping UK drivers. We have the skills and knowledge to keep your vehicle running.

Plus, with RAC Mobile Mechanics, you can avoid the hassle of taking your vehicle to a garage when you need a repair. We’ll come to you, at your home or work.

Close up of an RAC Mobile Mechanic underneath a car

RAC Mobile Mechanic

Our top pick

RAC Mobile Mechanic

At the RAC, we’ve got over 125 years’ experience in offering complete peace of mind to our members. We’re best known for our breakdown service. And now – our new RAC Mobile Mechanics are here to help make every day motoring easier. If you need a service or repair, they’ll come to you at your home or work.

Book a car diagnostic

Our mobile mechanics will spend up to 30 minutes checking your car for faults and talk you through any repairs you might need and give you a report for your records. There are various ways we can check for faults, which could include plugging in to check your car’s onboard engine management system.

We use original equipment manufacturer (OEM) standard parts, which means every new part will be the same standard and same quality as the original part it replaced.
Our mobile mechanics are friendly, honest, and backed by the RAC.
Close up of an RAC Mobile Mechanic running a vehicle diagnostic check

Book a repair

It’s easy to book a car repair online. We bring the garage to you with RAC Mobile Mechanics, or find a trusted local garage. Common repair jobs include:

We diagnose and repair clutch issues – whether your clutch is heavy or slipping, or you’re having trouble changing gears.
We check and correct alternator faults to keep your charging system running smoothly.
Oil is vital to a healthy engine, so it’s important to change it regularly.
If your brakes are making noise or you’re noticing reduced stopping power, it’s likely time to replace your brake pads or discs.

Introduction

If you own a car and want to keep it running smoothly, it’s a good idea to regularly perform a car diagnostic. Understanding car diagnostics saves you time, money, and hassle by catching problems early.

What are car diagnostics?

Car diagnostics use specialised tools to check your vehicle for any issues. They test problems in the engine, transmission, exhaust system, brakes, and more.

What does a car diagnostic include?

A car diagnostic test usually includes a range of system checks:

  • Engine check: Finds issues with the engine’s performance.
  • Transmission test: Makes sure the transmission is working as it should.
  • Exhaust system check: Finds leaks or other problems.
  • Brake system test: Checks the brake pads, discs, and fluid levels.
  • Airbag system check: Checks that the airbags will deploy correctly.
  • Electronic system test: Looks for faults in electronic components like sensors and on-board computers.

Remember – different mechanics may carry out different checks to what’s mentioned above. Ask your mechanic what they’ll be doing and make sure you’re getting any specific concerns looked at.

What do car diagnostics tell you?

A car diagnostic gives you info about the state of your vehicle. This can be helpful for several reasons. Your diagnostics will help you:

  • find issues early before they become serious
  • make sure all parts are working efficiently
  • confirm that critical safety systems are in good working order
  • save you from expensive repairs by dealing with minor issues early.

When do I need a diagnostic?

Consider a car diagnostic if you have:

  • Warning lights: A dashboard warning light comes on.
  • Performance issues: You notice a drop in performance or fuel efficiency.
  • Unusual noises: Your car makes strange noises.
  • Regular maintenance: During routine services to make sure everything is working correctly.

Just so you know, mechanics may vary in their checks. Talk to yours to understand their process and make sure any special concerns of yours are covered.

Car diagnostics cost

The cost of what you will pay for a car diagnostic varies. It’s usually based on the vehicle type and the issues being checked. It also depends on the location of the service provider. Just remember to speak with your mechanic to get an accurate estimate.

Frequently Asked Questions on car diagnostics

The cost you pay can vary depending on the type of car and how complicated the diagnostic test. Check with your mechanic for a quote.

Yes, a diagnostic test may save you a lot of money. It finds issues early before they become costly repairs. It can also keep your vehicle running efficiently and safely.

While you can buy a diagnostic tool, interpreting the results needs expertise. It’s best if you to have a professional mechanic perform the test.

Diagnostic tests take from 30 minutes to a few hours. This depends on what issues are being looked at.

Common diagnostic trouble codes include:

  • P0300: Random/Multiple Cylinder Misfire Detected
  • P0420: Catalyst System Efficiency Below Threshold
  • P0171: System Too Lean (Bank 1)

These are general examples, so your car may have different codes. Always check with a mechanic so you get an accurate diagnosis.

Yes, they are. Regular diagnostics can help keep your car in good health. It makes sure that underlying issues are addressed quickly, so you can drive with peace of mind on the road.

Again, keep in mind that mechanics might have their own checklists. Chat with your mechanic to be sure that they address any specific issues you have.