A warning light letting you know your DPF is blocked should not be ignored, but can in many instances be remedied by driving in a way which initiates passive/active regeneration of the DPF. Driving for over 10 minutes at speeds in excess of 40mph will often be sufficient to clear the blockage and regenerate the DPF.
Active regeneration
In which case it should be possible to complete a regeneration cycle and clear the warning light by driving for 10 minutes or so at speeds greater than 40mph.
Regeneration. Some say driving at speeds of over 40mph for 10 minutes using at least 2500 RPM and sticking in 3rd/4th gear can turn off your DPF light from your dash.
All you have to do is get your car on an A road or motorway on a regular basis, such as every 300 miles. You then need to run it for 10-20 minutes at speeds in excess of 40mph. This will heat up your exhaust and burn off any soot in the filter.
The easiest and cheapest method of DPF filter cleaning is by driving the vehicle for a long-distance at high revs per minute. Doing this increases the heat of the exhaust and burns the soot blocking the DPF filter. It's best to drive on a motorway or A road where you can keep the vehicle at a consistent speed.
It's not impossible to clean a DPF at home. But the risk is high. The filter is a very delicate component of your car. You can easily damage it during DIY cleaning.
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.
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.
Low speed regeneration is achievable including driving in Low Range. The typical minimum vehicle speed to enable regeneration is 30-40km/h and the higher engine load will assist reaching the minimum exhaust temperatures to enable regeneration of the DPF.
If this happens, just carry on driving, keeping your engine speed above 2,000 revolutions per minute and shifting down if necessary. The filter-cleaning process will start - and we recommend you don't stop the journey or switch off the engine until it's finished.
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.
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.
At some pre-determined blockage level, it triggers an active regeneration - if the driving conditions are right. Typically you'd need to be driving at more than about 80 kays an hour (50mph - 'Murica), and you'd need to be in a high gear, like fourth, fifth or sixth in a six-speed auto.
When the accumulating soot reaches about 45%, the DPF switches to active regeneration. The car forces higher exhaust temperatures, burning the soot in the process.
How long does DPF regeneration take? Passive regeneration will take around 30-50 minutes to complete at speeds over 40mph, while active regeneration can be completed in as little as 10 minutes at the same speeds.
A blocked DPF or obstructed exhaust will force your engine to work harder to expel exhaust gases, reducing available power and increasing fuel consumption.
Signs of a clogged DPF include reduced engine performance, increased fuel consumption and exhaust emissions… or simply the display of the DPF light in your cockpit.
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.
Using Redex DPF Cleaner (either when your light comes on or regularly as a preventative measure) will help the soot to burn away during normal driving, so that your filter clears, and the light stays off. This can save you a lot of time, money, and stress, as a new DPF will typically cost around £1,000.
The most common reasons for DPF blockages are: Short journeys where the engine doesn't reach optimum operating temperature; Clogged EGR Valve increasing diesel soot passed to the DPF; Faulty fuel injectors sending too much fuel to the air/fuel mixture; Incorrect engine oil upon servicing the car ; Turbocharger failure ...
Drive over 40 mph (64 kph) to begin active regeneration.
Begin driving and pay attention to both the engine and vehicle speed. Try to keep the engine speed around 2500 rpm. Active regeneration increases the temperature in the DPF to turn the particles into gas which can be expelled.