Will a remapped car pass MOT?

A fully developed ECU remap will pass a UK MOT. Current MOT regulations require that diesel engines are tested using an opacity test to measure smoke density, and petrol vehicles are tested for Carbon Monoxide (CO), Hydrocarbons (HC) and lambda values (λ). A fully developed ECU Remap will meet all of these requirements.

In countries with stricter emissions testing, a professionally developed remap, such as that from Celtic Tuning, will still pass, providing the vehicle is in good running order. Poor ECU Remaps can result in increased smoke, increased hydrocarbons and possible malfunction indicator light (MIL).

When a quality ECU remap has been installed, MOT failures are usually caused by vehicle issues rather than the remap itself. Common faults, such as boost leaks, fuelling faults, such as worn injectors, are all things that can be a result of wear and tear over the life of the vehicle.

It is important to highlight emission delete software here. Options such as DPF deletes, EGR deletes, and AdBlue deletes will result in an MOT failure. This modification is illegal to use on public highways and can result in a fine if detected. In many foreign countries, there are additional diagnostic checks carried out to detect such software, and it should only be for off-road/motorsport use.