Does remapping void your warranty?

This is the question we get asked before every other question about re-mapping, and it deserves a straight answer rather than one of the two you usually get — that it is completely fine, or that it destroys everything. Neither is true.

What a warranty can and cannot be withdrawn for

A manufacturer warranty is a contract to fix defects in the car as they built it. A re-map changes how they built it, so what happens next depends on what broke and why.

If a door mirror motor fails, a re-map has nothing to do with it and refusing that claim would be difficult to defend. If a turbo fails, or a clutch, or a dual-mass flywheel, or a gearbox, the manufacturer will point at the extra torque and decline — and in most cases they will be within their rights to.

So the practical rule is not that the warranty is void. It is that the driveline has become your problem. On a three-year-old car with a year left to run, that may be a trade you are happy to make. On a six-month-old car it usually is not.

Can they actually tell?

Yes, and it is worth being blunt about it because plenty of people are told otherwise. Writing a file to an ECU updates a write counter and changes the checksum of what is stored on it. A main dealer running a diagnostic session can see that the software on the car is not the software the factory put there.

There are shops that will tell you their file is undetectable. Assume it is not, plan on that basis, and you will never be caught out. The sensible approach is not to hide a re-map — it is to know what it exposes and decide with your eyes open.

Insurance is the bigger risk, and the cheaper one to fix

This is where re-mapping genuinely costs people money, and it is entirely avoidable. A re-map is a modification. Every UK policy asks about modifications. Failing to declare one gives an insurer grounds to treat the policy as misrepresented — which can mean a refused claim on a car written off in an accident that had nothing to do with the extra power.

• Tell them before you book, not afterwards. It costs nothing to ask what the premium becomes.
• Get the figures in writing from us — power and torque, before and after. That is what an underwriter actually wants to see.
• Expect a small increase rather than a refusal. Most mainstream insurers note a Stage 1 without much drama; a few decline it, and there are specialists who do not.
• Declare it at renewal too. A modification you mentioned once in year one does not carry itself forward automatically.

We give every customer the before and after printout for exactly this reason. It is a two-minute phone call to your insurer, and it is the difference between a modified car that is covered and one that is not.

Finance, PCP and lease agreements

A separate question, and the one people forget. If you do not own the car outright, you have agreed not to modify it, and a lease or PCP return inspection is where that surfaces.

This is the strongest argument for keeping the original map, and it is why we read and save yours before writing anything and keep it on file indefinitely. Putting the car back to exactly how it left the factory is a short job rather than a rescue mission — and on a leased vehicle that is not a nicety, it is the whole answer.

What we will not do, and why it belongs in this article

We do not remove DPFs, EGR valves or AdBlue systems. Not as an add-on, not quietly, not for anybody. It is an MOT failure and illegal for road use, and a car that has had its emissions equipment removed is worth less and harder to sell.

It is worth saying here rather than on the re-mapping pages, because the shops that will do it tend to be the same ones telling you a re-map is undetectable and your insurer does not need to know. All three claims come from the same place.

So should you do it?

If the car is out of warranty, owned rather than financed, mechanically healthy and declared to your insurer, a Stage 1 file is one of the better-value things you can do to it — typically 15 to 30 per cent more power and torque on a turbocharged engine, with no hardware changes at all.

If it is a new car under a manufacturer warranty, or on a lease you have to hand back, wait. The file will still be available in two years, and by then the car will not be somebody else's to worry about.

Send us the registration and we will tell you what the engine actually gains, where your warranty stands, and what the health check finds before anything is written. We re-map in Milton Keynes and across Bletchley, Newport Pagnell, Buckingham and Leighton Buzzard.