Diesel Particulate Filters – what you need to know

At EAC Telford we’re keen to ensure you have trouble free motoring in a car you can trust. We receive a fair number of enquiries for DPF faults so thought it’d be a good idea to give you the information you need to know to keep yours healthy.

Since 2009 Diesel Particulate Filters (DPFs) have been fitted to diesel cars in a bid to cut pollution. Unfortunately, they can become blocked up causing some very expensive engine damage problems.

What is a DPF?

Diesel engines generate soot particulates, which can lead to respiratory problems and the risk of heart disease. The aim of the Euro 5 legislation that led to the need for DPFs to be fitted is to cut 80% of particle emissions. But DPF technology has led to garages having to tackle the problem of cars whose DPFs have become blocked.

It’s important that a car’s DPF is cleared out regularly. This process is known as ‘regeneration’. In general, it’s dealt with passively when the exhaust’s temperature is high enough. In normal circumstances, this requires a car to be driven on the type of road where the vehicle can run smoothly, for example, motorways, fast dual carriageways or clear A-roads.

This enables the soot to be burned off so only a small amount of ash residue is left behind. Issues arise because this ash builds up over time and cannot be removed without the DPF being dismantled.

Common Causes of Failure?

Many cars are driven mainly in towns and can’t benefit from being used on the open road, which would allow them to perform passive regeneration. This is why they are fitted with ‘active’ regeneration systems that enable the engines to control the regeneration process with software that monitors if the DPF is becoming blocked. If this is the case extra fuel is injected into the engine to boost the exhaust gas temperature, so triggering the regeneration.

Regeneration should occur every 300 miles or so. It takes between 5 and 10 minutes to complete. However, when journeys are too short and the regeneration is interrupted which may cause:

  • The cooling fans to come on
  • The engine to idle faster
  • The automatic Stop/Start mechanism to stop working
  • Increased fuel consumption

If any of these things happen don’t ignore warning lights, which may be indicating the DPF is blocked. If this is the case you need to drive the car for over 15 minutes at more than 40mph continuously to trigger the regeneration process. You’ll find the specific instructions for your vehicle in the driver’s handbook.

Diesel Particulate Filters

Continuing to drive slowly in traffic is not an option as it will cause the soot to build up and could trigger the car’s ‘limp mode’ to prevent any further engine damage. You should take the car to a garage where they can carry out the filter regeneration. If the filter needs replacing it can cost a four-figure sum including labour. In most cases, it does not take long for a partially blocked DPF to need emergency regeneration.

Why is a DPF required?

The stipulation that a diesel car needs to be fitted with a DPF came in European emissions regulations 10 years ago. It is now an offence to drive any car that does not comply with prescribed emissions standards. Plus DPF removal can invalidate a car’s insurance cover.

How To Avoid A Big Bill?

So… if your DPF light is on and remains lit after you’ve followed the instructions in your handbook for regeneration (driving on a dual carriageway etc), what next?

We’re keen to keep any remedial work to a minimum which is why accurate diagnosis is essential. There are a number of subsystems that are required for efficient regeneration (glow plugs, additive injectors etc), it’s very common for one of these to have caused the fault.Once we’ve found the root cause we can then assess if cleaning the DPF is suitable.

At EAC Telford we have a lot of experience in DPF repairs. You’ll be guaranteed a high level of workmanship and great value.

Call today with you DPF faults. We’re here to help on 01952 980566