A car diagnostic in the UK costs roughly £25 to £120. Most sit between £50 and £100. The national chains advertise £39.95 to £99 for a plug-in check, and mobile mechanics who come to you are around £99 to £104. The cheap end is a code read. A longer fault-find costs more because it takes more time.
Those are advertised prices we checked ourselves on 28 October 2026, with a link to every page we took them from. Below is who charges what, what you actually get for the money, and how to avoid paying twice for the same answer.
What the big UK names charge
All five prices below were read directly from each company's own website on 28 October 2026. Prices change, so follow the link if you are booking.
| Provider | Advertised price | What that buys | Source, checked 28 Oct 2026 |
|---|---|---|---|
| Kwik Fit | £39.95 | A fault code check on an OBD2 scanner, at Kwik Fit Plus centres. Their page states that if further investigation into the causes is needed, additional costs may occur. | kwik-fit.com |
| National Tyres and Autocare | £64.99 | A Diagnostic Health Check that scans the modules across the car, engine, gearbox, ABS, immobiliser and more. Their page says it does not include repairs, and that if they cannot carry out the repair they give you the codes to take to a specialist. | national.co.uk |
| Halfords | From £64.99, and the page says the price is based on your nearest garage | A diagnostic check at an Autocentre, taking up to an hour. Their page says that if more time is needed they will ring you for approval and additional charges may apply. | halfords.com |
| The AA | £99 | Thirty minutes of fault finding from a mobile mechanic at your home or work, with a written report. Repairs are quoted separately. Availability is limited to certain areas. | theaa.com |
| RAC | Average £104, varying by make and by town | Up to thirty minutes with a mobile mechanic, plus a report. The £104 is the RAC's own average, taken from mobile mechanic quotes between 1 January and 31 March 2025, so it is their figure and it is dated. | rac.co.uk |
Two things worth saying plainly. Kwik Fit's £39.95 is advertised at Kwik Fit Plus centres rather than every branch, so ring your local one first. And some franchised dealers charge considerably more than any figure in this table, often billed as diagnostic labour by the hour, but we could not find a published price on their own websites, so we have left those numbers out rather than quote a figure we cannot stand behind.
What an ordinary independent garage charges
The chains are the easiest prices to find, but most cars in the UK are looked at by independent garages. Three sources, all checked on 28 October 2026:
- £25 to £120 is the spread of actual diagnostic bookings made through BookMyGarage over the previous twelve months, across more than 2,100 garages. Their page gives that range as last updated on 20 October 2026, which makes it the freshest figure we found.
- £57.21 is the average diagnostic test booked through FixMyCar. Their page carries an August 2025 date, so treat it as a little older.
- £50 to £100 is the UK average according to Kwik Fit's own guide, which is a useful cross-check because it is a garage chain describing the wider market rather than selling against it.
Put together, a straightforward diagnostic at a local garage is usually somewhere in the £40 to £75 bracket, and you reach £100 or more when you are buying a mechanic's time at your front door or a longer investigation on a difficult fault.
Why one diagnostic is £39.95 and another is over £100
This is the part most price comparisons skip, and it matters, because the cheap one and the dear one are not the same job.
A code read is a scan. A technician plugs a reader into the socket under your dashboard, pulls the stored codes out of the car's computers and tells you what they say. It takes minutes. That is what £39.95 buys, and it is a fair price for it. Kwik Fit are upfront about the limit: their own page says that if further investigation into the cause is needed, that costs more.
A diagnostic check is bench time. At around £65 you are buying up to an hour. That is long enough to scan every module rather than just the engine, to separate current faults from historic ones, and to form an opinion. Halfords say outright that if it takes longer than the hour they will phone you for approval first.
A fault-find is a mechanic's time on your car. At £99 to £104 a mobile mechanic comes to you, asks what the car has been doing, may take it out on the road, and writes up what they found. You are paying for the person, the travel and the judgement, not for the scanner.
None of that is a rip-off. A stored code points to a system, not always the exact part, and the work of turning a code into a repair is real work. An intermittent electrical fault can genuinely eat two hours before anyone touches a spanner. The honest summary is that the cheapest option answers the smallest question, and most of the money in a diagnostic bill is time.
Questions worth asking before you book
- Is this a code read or investigation time? Ask how many minutes are included.
- What happens if it takes longer? Ask whether they ring you first, as Halfords and Kwik Fit both say they do.
- Is the diagnostic fee deducted from the repair if I go ahead with you? Many garages do this and will not mention it unless asked.
- Will I get the actual code numbers in writing? You want them. They are yours, and they let you get a second opinion or a quote elsewhere without paying for the scan twice.
What a remote diagnosis cannot do
We sell a remote service, so it would be easy to tell you it replaces all of the above. It does not, and anybody who says otherwise is selling you something.
A mechanic reading your codes and symptoms by email cannot:
- Put the car on a ramp and look underneath it.
- Drive it and feel what it is doing.
- Take a live reading, watch the sensor data while the engine runs, or scope a signal.
- Smoke test for an air leak, pressure test a cooling system or do a compression test.
- Hear it, smell it or see the oil on the floor.
- Clear the fault, reset the light or fit the part.
Some faults need a ramp and a road test, full stop. If your car is unsafe, undrivable or the engine warning light is flashing, book a garage and do not wait on an email.
Where a £20 remote read fits
Here is the honest version. A remote diagnosis is not a replacement for a garage diagnostic. It is the step before you commit to one.
If you have already plugged in a reader, or a garage has given you your codes, you are holding information you cannot interpret and they can. Quick Diagnosis is £20, and it is a professional read on the codes and symptoms you already have: the most likely causes, in order, and what to check first. Sometimes that is enough on its own, because a small fuel vapour leak really can be a petrol cap that is not sealing. More often it tells you whether you are likely looking at a cheap sensor or a catalytic converter, and what sort of garage to take it to, before you pay anyone for a ramp.
It is read by one mechanic, personally, not an automated code lookup. If we cannot help, you do not pay. You can also look your code up free on the fault code decoder first, and come to us only if you still want it narrowed down.
We usually reply within one working day, Monday to Friday.
Prices in this article
These are advertised prices and published averages for guidance only, read from each source on 28 October 2026 and linked above. Actual prices vary by vehicle, by location and by how long the fault takes to find, and a stored code points to a system, not always the exact part. Check with the provider before you book.
Written by the First Diagnostic mechanic
Over a decade in the trade. A VW-only workshop running diagnostics and electrical repair, then BMW-only through to full engine rebuilds. Now runs an independent all-makes workshop and builds and wires drift cars for competition, including trackside work as head mechanic. More about who reads your codes.