Car Diagnostics | Book a Car Diagnostic for your Mercedes

Trustpilot rating for all RAC Mobile Mechanics.

Why choose the RAC for a car diagnostic?

With RAC Mobile Mechanics, you can avoid the hassle of taking your vehicle to a garage. They can do a vehicle diagnostic check on your driveway, so you don't even need to leave the house.

When it comes to diagnosing issues with your vehicle, our friendly expert mechanics are here to help. We use state-of-the-art diagnostic equipment to accurately identify any problems, ensuring your vehicle runs smoothly and safely. The price includes the diagnostic service – no hidden costs. Just friendly, honest experts.

Close up of an RAC Mobile Mechanic underneath a car

Our top pick for your Mercedes

We’ll come to you at home or work

RAC Mobile Mechanic for your Mercedes

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

For a limited time, get £50 off repairs over £150 when you book a diagnostic test. Offer ends 09/12/25, 09:00.^**
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.

OEM quality parts

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.

Mechanics you can trust

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:

Clutch Replacement

We diagnose and repair clutch issues – whether your clutch is heavy or slipping, or you’re having trouble changing gears.

Alternator repair

We check and correct alternator faults to keep your charging system running smoothly.

Oil change

Oil is vital to a healthy engine, so it’s important to change it regularly.

Brake pads & Discs

If your brakes are making noise or you’re noticing reduced stopping power, it’s likely time to replace your brake pads or discs.

And it’s not just car diagnostics that we do for your Mercedes

Mobile mechanics bring the garage to you, saving you the hassle of getting your car to a garage. If you need a service or repair, they’ll come to you at your home or work.

A close up of an RAC mobile mechanic looking under the hood of a car

Try one of our RAC Approved Garages

View all garages

A1 Tyres and Exhausts

5.0/5

With over 30 years experience of automotive repairs in Coventry, A1 Tyres and Exhausts is a name that you can rely on to deliver a professional, high quality, and reliable service, that will meet all of your car needs. And above all, we are a name you can trust again and again.

Unit 12-13, Relton Mews, Coventry, CV65HE

New Garage (Harnham)

5.0/5

New Garage (Harnham) ltd was established in 1984 and has been providing quality vehicle repairs and servicing in the Salisbury area for over the past 30 years. Our 4 highly trained and experienced mechanics/technicians have over 90 years of combined experience between them working on motor vehicles. We work with all makes and models and specialise in Electric and hybrid vehicles; the technology for these vehicles has been developing greatly over the last 20 years and we have kept up to date with all the technology, tools and training to be able to repair and service electric/hybrid vehicles of all makes and models. We are an RAC Approved garage and we only use high quality parts and all parts and labour we provide come with a standard 12-month warranty for added peace of mind. If you need your car picked up, a lift home or a courtesy car please let us know and we will do all we can to assist you. We look forward to hearing from you.

28-30 Harnham Trading Estate, Salisbury, SP2 8NW

Acton Service Centre

4.2/5

Acton Service Centre came under new management in 2012. A family run business that prides itself in offering excellent customer service and professional workmanship. Our highly trained engineers and technicians are committed to providing you with the solution to all your motoring needs. Based in Acton just off the A406, our modern reception and viewing area has been newly designed for the comfort of our large base of loyal customers.

17-18 The Broadway, Gunnersbury Lane, Acton, W38HR

Kncustoms LTD

4.1/5

Kncustoms LTD are based in Sheffield offering the best possible service to all our customers from the more basic servicing to the extreme - an engine change. We pride ourselves in offering the best customer satisfactory, and going the extra mile!

Unit 1 And 2 Acers Hill Lane, Acers Hill Lane, Sheffield, S94TY

California car and commercials Ltd, Bosch Car Service

4.4/5

We are a established MOT and service centre run by two brothers with a combined experience of 15 years in the motor trade. Our new site on Garrard Way, Kettering consists of 5 service bays and a class 4, 5 & 7 MOT bay. Our aim is simple, to be a one stop shop for all your motoring needs. Wether it be your annual MOT and service or more major work our highly experienced staff are on hand to help. We have a clean, modern premises with state-of-the-art technology and equipment including the most up to date Snap-On class 4, 5 & 7 MOT bay. We run our own fleet of recovery vehicles so collection and delivery is always available. Feel free to call Tony or Mario for any of your vehicle needs

Garrard Way, Telford Way Industrial Estate, Kettering, NN168TD

Frequently asked questions on car diagnostics

How much does it cost to diagnose a car problem?

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.

Is a car diagnostic test worth it?

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

Can I do a car diagnostic myself?

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.

How long does a car diagnostic test take?

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

What are common car diagnostic codes?

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.

Is a car diagnostic test necessary for a service?

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.