Key takeaways A remap is not illegal in itself, but removing or disabling emissions equipment is a different matter. On a diesel built with a particulate filter, a missing DPF fails the MOT, and GOV.UK says removing one is almost always illegal. The official DVSA guide on modifying emissions has been withdrawn for review, so always check current rules. A reputable tuner leaves every emissions system in place and working. People often ask whether chiptuning is legal in the UK. Changing engine software is not the problem. What matters is what the changes do to your car's emissions equipment. This guide uses official GOV.UK sources to explain where the line sits, so you can judge what a tuner is really offering you. What the MOT checks Since February 2014, the MOT exhaust inspection on diesel cars has included a check for the diesel particulate filter, or DPF. According to the government announcement of that change , a car that was fitted with a DPF as standard fails if the filter has...
Chiptuning and ECU remap guides: how it works, what you can gain, the risks and how to choose a good tuner.