If you ignore a DPF warning light and keep driving in a relatively slow, stop/start pattern, soot will build up in the filter until your car goes into 'restricted performance mode' to prevent damage. If you let it get this bad: Driving at speed alone won't be enough.
While your vehicle won't stop running the moment the light turns on, continuous driving can lead to more severe issues like decreased fuel efficiency, reduced performance, and in the worst case, engine damage. An illuminated DPF light will cause an MOT failure.
Never ignore your DPF warning light. You will have little time between the point where the DPF is minimally blocked, and the point where manual regeneration is the only solution. And if you fail to have the manual regeneration done, it is very possible that you will need a new engine.
The worst thing you can do is to ignore the warning light. Doing so will mean soot will continue to build up, ultimately leading to the vehicle's computer to go into limp mode to prevent more damage. Limp mode limits a vehicle's speed in an effort to reduce the amount of soot being sent through the filter.
It's a failure to correctly regenerate that is the cause of most diesel particulate filter issues: they become blocked, which increases exhaust emissions, stifles engine performance and sometimes even puts the car into a restricted 'limp-home mode'.
Sometimes, a hot and pungent smell can also start coming from your engine as the soot is being burned away. Your stop / start function may also deactivate. Driving for 15 minutes as speeds above 40mph should provide your DPF filter with enough heat to burn away the soot by itself.
Nevertheless, a general rule of thumb to follow is that you should run the engine at least 40 mph and at least 2500 rpm. Ignoring the DPF light, or failing to clear the blockage in a timely manner, will lead to continued soot build up in the DPF.
Low engine RPM
Alongside the engine not producing much power, the engine may not be able to rev very high, sometimes reaching a top RPM of 3,000. This is a consequence of both the exhaust gases restricting the engine's usual cycle, and because of the lack of turbo pressure.
High Idle Times. High idle causes' buildup of particulates in the filters, which increases the cleaning frequency. Particulates not burned off through the regeneration process can lead to poor fuel economy, reduced power output and possibly costly engine damage.
The DPF regeneration process creates very high exhaust gas temperatures and the exhaust will radiate a considerable amount of heat during and after DPF regeneration, and after you have switched the engine off. This is a potential fire hazard.
Most engine management systems will actively regenerate the DPF when the car is driven at speeds above 40mph for around 10 to 15 minutes. The soot particles trapped in the filter will soon burn away and the warning light should switch off.
Protecting Equipment. Today's aftermarket equipment makes it even more important to reduce idling. When idling, the vehicle is not operating at the ideal temperatures that allow soot to burn off the diesel particulate filter (DPF).
But diesel engines have a range of systems to reduce their emissions, including a diesel particulate filter (DPF), and DPFs can block and cause costly issues. Diesel engines are built for high-mileage drivers, and aren't really suitable for lots of short journeys.
Active regeneration will be initiated every 300 miles or so depending on how you use your car and will take 5 to 10 minutes to complete. But it's a problem if your journey's too short and the regeneration doesn't finish. During active regeneration you may notice: Cooling fans running.
A blocked DPF or obstructed exhaust will force your engine to work harder to expel exhaust gases, reducing available power and increasing fuel consumption.
When the volume of soot and ash inside a DPF increases, the back pressure rises, which produces a higher load on the engine to force the exhaust gases through the DPF. This uses more fuel and causes the vehicle to require more frequent regenerations, each of which consumes fuel.
Once blocked though, turbo failure can occur very quickly. If you don't check for a DPF issue when installing a replacement turbo, there is a very high chance the replacement turbo will suffer the same failure, as it will be subject to the same operating environment as the previous unit.
If you notice a reduction in the car's power, acceleration, or fuel efficiency, then it is likely time to get your DPF checked. If your car is emitting more smoke than usual, it could be a sign that the DPF is clogged and needs replacement. A blocked DPF can also cause a foul odour to emanate from the car's exhaust.
Both active and passive regeneration happens automatically, without the intervention of a mechanic or DPF specialist. Forced regeneration – If neither of the above methods work, the garage will need to clean the blocked DPF. This will cost between £85-100 for a straightforward job or as part of regular maintenance.
If the journey is too short or the vehicle does not have enough fuel the DPF regeneration process might not work. To allow the DPF to regularly regenerate it's advised the fuel tank is more than a quarter full, otherwise, the vehicle will opt to save fuel instead of redirecting it for DPF regeneration.
The main reason is that, first and foremost, it is highly illegal. Removing any emissions device on a diesel engine or adding a non-SMOG-compliant product carries a punishment of up to a $5,000 fine per unlawful part installed.