Vehicle Diagnostics

Vehicle Diagnostics – Engine Fault & Warning Light Diagnosis in Slough

Car Servicing – Interim, Full & Major Car Service

We specialise in accurate and efficient vehicle diagnostics for all makes and models. Whether you’ve noticed a warning light on your dashboard, experienced a sudden drop in performance, or heard unusual noises, our technicians have the expertise and tools to get to the root of the problem quickly.

Our state-of-the-art diagnostic equipment can read and interpret fault codes from your car’s ECU (Engine Control Unit) and identify issues in key systems such as the engine, gearbox, brakes, suspension, and more. We don’t just stop at reading the codes – we investigate the underlying cause so you get the right repair the first time.

Customers across Slough trust Onyx Performance for diagnostics because we combine technical skill with honest advice. We explain faults clearly, recommend only the necessary repairs, and always use high-quality or OEM parts for any work carried out. This means you can get back on the road knowing your car is running smoothly and safely.

Why Choose Onyx Performance?

As Seen on Carwow

We’ve been proudly featured on Carwow – a testament to the quality, professionalism, and performance-focused results that set us apart. Watch our feature here to see us in action.

Expertise You Can Trust

With years of experience and deep technical knowledge, our team understands performance vehicles inside and out – from custom remaps to high-end servicing.

Advanced Workshop & Tools

We operate from a state-of-the-art facility in Slough, equipped with cutting-edge diagnostics, dyno testing, and industry-leading tools for accurate, high-quality work.

Tailored Solutions for Every Vehicle

We don’t believe in one-size-fits-all. Every car gets a bespoke approach, ensuring the best results whether it’s a remap, upgrade, or routine service.

Trusted Nationwide

Performance enthusiasts from across the UK come to Onyx because they know they’ll receive premium-quality workmanship, careful attention to detail, and honest advice.

Complete Care, All in One Place

From tuning and servicing to tyres, trackers, and immobilisers – we offer a full suite of services under one roof, all with a strong focus on safety, reliability, and top-tier customer support.

Customer Reviews

    
 
 
       Posted on Google  
   
   Mark Wiltshire 
 
 
 
 Trustindex verifies that the original source of the review is Google. Professional yet friendly, very helpful would recommend 👍
  
 
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   Paul Forrester 
 
 
 
 Trustindex verifies that the original source of the review is Google. Nice refurbishment of my alloys
  
 
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   Noel Kerins 
 
 
 
 Trustindex verifies that the original source of the review is Google. Excellent service, great quality job on 2 of my black alloys. They also did my father & husbands cars too. Great value for money and a special thanks to Ben.
  
 
      Posted on Google  
   
   Jamie Taylor 
 
 
 
 Trustindex verifies that the original source of the review is Google. Had my golf R mapped and tuned to stage 2 very impressed with the work they done Ben and Sam great guys very friendly and very professional would recommend 👍🏻
  
 
      Posted on Google  
   
   DSK 
 
 
 
 Trustindex verifies that the original source of the review is Google. Brought my Audi S3 in for a Stage 3 tune with a bigger turbo and full supporting mods. Things didn’t start smoothly — the Falcon turbo I had fitted from eBay turned out to be faulty and smoked heavily on the dyno.Instead of rushing the job or giving me attitude, they helped me swap it out for a proper Garrett PowerMax and carried on professionally. Then I ran into fueling problems caused by another low‑quality eBay part, and again they took their time, diagnosed the issue properly, fixed it, and made sure everything was right before continuing.After all the setbacks, they still mapped the car, spent a lot of time on it, and didn’t charge me anywhere near what the work was worth.They showed patience, honesty, and real skill. Very happy with the service and the way they looked after me.
  
 
      Posted on Google  
   
   randip 
 
 
 
 Trustindex verifies that the original source of the review is Google. Highly recommended. Fitted my catless downpipe and full exhaust on my Audi RS7. The sound is amazing!

The staff were very friendly and kept me updated at every step of the process
  
 
      Posted on Google  
   
   Dan Simmonds 
 
 
 
 Trustindex verifies that the original source of the review is Google. This is the second time I have used Onyx Performance first time for wheel refurbishment and last time for remap and i would use their services again in the future without a doubt. They are very knowledgeable about what they specialise in, they are polite and you can see they care not only about what their customers want to do but also about what they can offer the customer. Thanks to the OP team.
  
 
      Posted on Google  
   
   Taranjit Lehal 
 
 
 
 Trustindex verifies that the original source of the review is Google. Took my Mercedes C200 to Onyx performance for a stage 1 remap, my car is much quicker and throttle response is much better than before the remap. They also advise you about power and gains and the maps are tailored for your specific car and model, no stress on engine or gearbox. Thank Onyx , Brilliant work.
  
 
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   Carlos fernandez 
 
 
 
 Trustindex verifies that the original source of the review is Google. Absolutely fantastic service friendly customer service will definitely be going back for further modifications 5 star service do not go anywhere else other than onyx😎🙏🏼
  
 
      Posted on Google  
   
   Aurimas Gercas 
 
 
 
 Trustindex verifies that the original source of the review is Google. Great service, recommend.

Book Your Vehicle Diagnostics in Slough Today

Don’t ignore that warning light – it could be a sign of something serious. At Onyx Performance, we provide professional vehicle diagnostics in Slough using advanced equipment and expert analysis. Book today and find out exactly what’s going on under the bonnet.

5-Star Google Reviews

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Why Choose Onyx Performance for Servicing?

Experts in Performance Cars

We know how to properly care for performance, modified, and luxury vehicles. Our team has the skills and experience to handle specialist requirements confidently.

Correct Service Schedules

Every service follows the exact schedule recommended by your vehicle’s manufacturer, helping maintain performance and protect your warranty.

Quality or OEM Parts

We only use high-quality aftermarket or original manufacturer parts, ensuring long-lasting reliability and top-level performance.

Full Vehicle Inspection

Our service goes beyond just changing oil. We inspect all key systems to keep your car safe, smooth, and road-ready.

Honest Advice, No Surprises

With transparent pricing and expert recommendations, you’ll always know what your car needs – no upselling, no hidden fees.

Fast, Trusted & Tracked

We offer quick turnaround, maintain service records, and send reminders – that’s why customers travel to us from across the UK.

Frequently Asked Questions

What does a vehicle diagnostic check involve?

A diagnostic check uses specialist equipment to read your car’s ECU fault codes and assess the health of various systems. At Onyx Performance, we go beyond code reading – our technicians also carry out physical inspections to confirm the exact cause of any issue.

How long does a diagnostic test take?

Most diagnostic checks take between 30 minutes and an hour, depending on the fault. If the problem is more complex, we’ll keep you updated and explain what’s required before carrying out any further work.

Can you diagnose all types of warning lights?

Yes – we can diagnose all dashboard warning lights, including engine management, ABS, airbag, and gearbox lights. Our tools work with all makes and models, including performance and modified vehicles.

What happens after you diagnose the fault?

Once we’ve identified the issue, we’ll explain it in plain English, provide a detailed repair recommendation, and give you a transparent quote. We’ll never proceed without your approval.

Do I really need a diagnostic check if my car still drives fine?

Yes – some faults can cause hidden damage if left unresolved. Even if your car feels normal, a warning light usually means there’s an issue that needs attention before it becomes more serious or costly.

Will a diagnostic check fix the problem?

A diagnostic check identifies the cause but doesn’t fix it directly. However, we can carry out the necessary repairs on-site, using high-quality parts and manufacturer-approved methods to restore your car’s performance.

Get a quick quote

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