Slough's specialists in
Engine Diagnostics.
Real engine diagnostics with main-dealer level kit. Root cause, not parts cannon. No nonsense. No hidden prices. Book in today.
⭐⭐⭐⭐⭐ 4.9 out of 5 from 500+ Google reviews. Trusted by drivers across Slough since 2019
- ✓6 months interest-free, up to £3,000
- ✓Same-day slots available in Slough
- ✓Same trusted team. Every visit
Engine warning light, limp mode, intermittent misfire, mystery rough idle? Most cars that come to us for diagnostics have already been somewhere else, had a code cleared or a sensor swapped, and the fault came back the next morning. That's because a generic OBD reader sees about 5% of what's actually happening in a modern car. At Onyx in Slough we plug in manufacturer-level diagnostic equipment, read every module, and trace the fault to the actual cause.
Why book engine diagnostics with Onyx in Slough?
- Main-dealer level kit. for VAG, BMW, Mercedes, Ford, JLR, Toyota, Honda, Stellantis.
- Live data and freeze-frame. we read exactly what the ECU saw when the fault triggered.
- Scope work on hard faults. wiring breaks and sensor signal noise a scanner cannot see.
- Plain English report. no jargon, no 'computer says no'. You leave knowing what it is and what it costs.
- Spread the repair over 6 months. interest-free up to £3,000, first instalment at booking.
How we find the real fault
A diagnostic session starts with us listening to you. What's it doing, when, how often, what was changed recently. Then the car goes on the ramp with the diagnostic laptop plugged in. We pull codes from every module (not just the engine ECU), look at live data while the fault is happening where we can recreate it, and on hard faults we go to the oscilloscope on the actual wires. That's how you find a broken earth, a chafed signal wire, or a sensor giving plausible-but-wrong readings.
Common ones this month: a 2014 BMW 320d from Langley with a P0299 underboost code that two garages had replaced the turbo on (it was a split intercooler pipe), a 2019 A4 from West Drayton with a misfire that only happened on hot days (cracked coil pack, not a coil-on-plug at random), a Transit from a Colnbrook fleet stuck in limp mode (corroded MAF plug, not a new MAF). The pattern repeats: real diagnostics save you the cost of parts you didn't need.
Booked the same week. Drop the keys, leave the car, get a written quote before any repair work starts.
Got a light that won't clear, a misfire that comes and goes, or a car that's already had work that didn't fix it? Call 01753 439115 or WhatsApp 07393 580281 with your reg and a description of what it's doing. Call 01753 439115 or WhatsApp 07393 580281.
Engine Diagnostics in Slough and across Berkshire
Onyx Autocentre is based in Slough, Berkshire and we look after cars from across the SL postcodes every day. Whether you're driving in from central Slough, Uxbridgeor Gerrards Cross, we'll book your engine diagnostics around your schedule. Same Slough workshop, same trusted team, same standard on every engine diagnostics job.
All our services
Every service we offer at our Slough workshop. Tap a tile to find out more.
- Air Bag RepairsFind out more
- Alloy Wheel Crack WeldingFind out more
- Alloy Wheel RefurbishmentFind out more
- Alloy Wheel WeldingFind out more
- Auto ElectricsFind out more
- Body Kit FittingFind out more
- Boost Leak & Smoke TestFind out more
- CambeltsFind out more
- Car Air ConditioningFind out more
- Car BatteriesFind out more
- Car BrakesFind out more
- Car ExhaustsFind out more
- Car ModificationsFind out more
- Car RepairsFind out more
- Car Safety ChecksFind out more
- Car ServicingFind out more
- Car TyresFind out more
- Carbon CleaningFind out more
- Cheap Car TyresFind out more
- Clutch ReplacementFind out more
- Diesel Performance ECU TuningFind out more
- Diesel TuningFind out more
- Dyno TestingFind out more
- ECU RemappingFind out more
- Engine DiagnosticsFind out more
- Engine ManagementFind out more
- Engine RebuildsFind out more
- Engine TuningFind out more
- Fleet MaintenanceFind out more
- Gearbox ServicingFind out more
- Gearbox TCU RemappingFind out more
- Haldex ServicingFind out more
- Head Gasket RepairsFind out more
- In-Car EntertainmentFind out more
- Mechanical RepairsFind out more
- MOT Failure RepairFind out more
- Nitrogen Oxide (NOx) Sensor RepairsFind out more
- Number PlatesFind out more
- Oil & Filter ChangeFind out more
- Parking SensorsFind out more
- Powder Coating for Alloy WheelsFind out more
- SteeringFind out more
- SuspensionFind out more
- Timing Belt ReplacementFind out more
- Trade Alloy Wheel RepairFind out more
- Turbo Intake CleaningFind out more
- Van Repairs & ServicingFind out more
- Vehicle SecurityFind out more
- Wet Belt ReplacementFind out more
- Wheel BalancingFind out more
- Window TintingFind out more
What Our Customers Say
Rated 5 Stars on Google by drivers across Slough and Berkshire
"Highly recommend this garage. After contacting a few other garages who didn't want to take my car in for diagnostics, these guys were happy to help. They diagnosed and fixed an engine fuel leak issue professionally and efficiently. Great service and very reliable. I'll definitely use them again."
"Very nice experience at Onyx — they took me in immediately and completed the DRL module swap efficiently. I have no regrets and would highly recommend."
"I brought my car to Onyx after visiting many other mechanics who failed to sort out issues with my vehicle. The mechanics here clearly explained the issues with the vehicle and fixed them quickly. Amazing service and wonderful people, highly recommend."
"Max and Ben are extremely professional and did an excellent repair on my wife's car at a great price. Max spotted the problem within 6 hours, which 2 other garages could not detect."
"I took my car to Onyx and met Ben who was friendly and I got the problem diagnosed by Ben which I had a faulty water pump. I was quoted a reasonable price and got it replaced. I was satisfied and would recommend Onyx."
"Took my BMW here for an oil change and oil filter and the service was spot on. Really friendly team, got the car booked in quickly and the job was done properly with no hassle."
"These guys are always polite and welcoming. I've taken multiple vehicles here and the service received has been excellent."
"Had the front pads done here over the weekend. Second time in with Onyx and service has been top notch both times. On time, no hassle and cost effective. Highly recommend."
"Great service, sorted out my alloy refurb at a good price and quick turnaround. Top service, highly recommend."
"A great experience with Onyx who fitted a new clutch for my Fiat 500. Super quick, friendly and well priced. Would highly recommend."
"Very friendly, no hassle effective service. Definitely recommend and will use when I need to get my alloy wheels refurbished."
"Brought my Audi S3 in for a coolant leak — the part was on back order but they managed to source one in a couple of days. Massive thanks to Ben."
"My vehicle went in for a brakes job and Ben and the team at Onyx Autocentre did an amazing job. Highly recommended."
Spread the cost over 6 months, interest-free.
Big bill? Pay the first instalment when you book, then spread the rest across up to 5 more monthly instalments, interest-free. Available on jobs up to £3,000. No setup fees, no hidden interest. FCA-authorised through Payment Assist, soft credit check, decision in minutes.
- ✓ Up to 6 months interest-free
- ✓ Available on jobs up to £3,000
- ✓ First payment at booking, rest split monthly
- ✓ Soft credit check, decision in under 2 minutes
- ✓ No setup fees, no hidden interest
Other services you might need
Air-bag warning fixes, crash data resets and module repair.
TIG-welded cracked alloy repair in Slough. Pothole and impact damage put right by certified welders.
Diamond cut, full colour change and kerb-damage refurbs.
Cracked alloy welding, straightening and TIG repair.
From dead batteries to CAN-bus faults. We trace it, we fix it.
Boost leak and EVAP smoke testing in Slough. We find the split hose, cracked charge pipe or dodgy valve in minutes.
Same-day slots are limited this week.
Call or WhatsApp now and get engine diagnostics today. Slough, Langley, Colnbrook, Windsor, Maidenhead, Uxbridge and Gerrards Cross.