It is a question we get here at Belmont MOT time and time again. Will DPF removal fail an MOT? Before we answer the question let’s look at what the DPF is and what it does.

What is a DPF?

DPF is short for diesel particulate filter, it is an item that sits in the exhaust of diesel cars and cleans the gases before releasing them into the air. This cleaning process causes the filter to “fill up” and if it isn’t cleaned it gets blocked and can cause a number of serious faults. The first fault you would notice is the DPF light on your dashboard warning you of a fault. Normally a clean can remove this light and your car operates as normal. However, on the odd occasion cleaning doesn’t work as it is too full and considered failed.

You might be wondering why the DPF didn’t clean when it’s supposed to. Well, let’s look at how the cleaning process works with the filter. There are 2 different ways in which it can be cleaned and is all done automatically by the ECU of the car. The first involves injecting fuel into the filter when it is at a certain temperature, the fuel then mixes with the carbon inside the filter and burns off. The second is very similar but instead of injecting fuel, it injects a special fluid that has the same characteristics and performs the same task for the DPF. The cleaning process is called dpf regeneration. We’ve noticed that older, used cars, suffer with DPF issues as the first owner isn’t aware of how to use it.

Before the cleaning process begins a number of things need to happen.

  1. Your car needs to be at full operating temperature.
  2. You need to have at least 1/4 tank of fuel.
  3. Your engine needs to be over 2500 revs per minute for 15 minutes (more recommended)

Without these being met, your car will not request cleaning the DPF as it will not complete the process adequately. This is why diesel cars are now recommended for those who do plenty of motorway driving.

Will Removing it Fail an MOT?

A removal is an option that garages offer as replacing the DPF can be very expensive. However, as of 2014 the DPF is something that will be tested under MOT conditions.  The workings of the filter isn’t what is tested but checking for a filter and that it is intact is on the test. If the DPF is removed then you will fail your MOT test.

If you have been looking for an MOT in Liverpool then be sure to consider us here at Belmont MOT. You can always ensure a fair test as a proud member of the Good Garage Scheme.