Getting a car remap right

Plenty of drivers wonder whether their car could go a little better.

A remap changes the settings in the engine's electronic control unit (ECU) for better performance. Doing it well means sorting out your insurance, any warranty on the car and the law on emissions before the work. These notes are for drivers in the UK.

What a remap counts as

The Financial Ombudsman Service settles complaints between people and their insurers. It describes a modification as any change that is not part of the manufacturer's standard specification. It names ECU remapping as one example.

Modifications can lead to higher premiums. Policies usually set out terms for modifying a car. A driver who follows them keeps the cover valid.

Checking the warranty and finance first

Before booking a remap, it helps to read the terms of any warranty on the car and ask the provider how it treats changes to the engine.

If the car is on finance, the agreement may have its own terms about changes. The finance company can tell you what they are.

Keeping your insurance valid

The Ombudsman says drivers should tell their insurer about any modification, as soon as possible. If a driver claims without having done so, the insurer may say it would have charged more, or would not have covered the car at all.

Declaring a change does not always mean its value is covered. The Ombudsman has seen drivers pay more for cover and then find, at the point of a claim, that the modification itself was excluded. Reading the policy documents shows what is covered.

Buying a car that may have been remapped

A used car can come with changes made by an earlier owner. The Ombudsman says owners should tell their insurer about modifications even if they were made before they bought the car.

When you buy, the Ombudsman suggests asking questions and looking through the paperwork to find out whether the car has been changed. If you are unsure whether something counts, your insurer can tell you.

Staying within the law, and if a claim goes wrong

A diesel particulate filter (DPF) traps soot from a diesel engine's exhaust. DVSA says these filters have been fitted to all diesel vehicles since 2013.

It is an offence to use a vehicle modified so that it no longer meets the emissions standards it was designed to meet. GOV.UK says removing a DPF will almost always break this rule. The fine can be up to £1,000 for a car and £2,500 for a light goods vehicle.

Since February 2014, MOT testers have checked for the filter. A car built with a DPF fails its MOT if the filter is missing. DVSA has banned testers who passed cars they knew had no filter. It also says an undeclared illegal change like this could invalidate the insurance.

In one case the Ombudsman reports, a driver's policy was voided after an accident. The insurer found an ECU remap and exhaust retuning he had not declared. The Ombudsman found the insurer's decision fair.