Had the message below appear yesterday,so before I asked on here I thought I'd RTFM ,but all it says is "If this message appears the driver should carry out the regeneration procedure as soon as possible" Can't find that in the manual ...can anyone tell me please

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Generic answer below. My wife's VW Tiguan automatically does it and the engine area gets VERY hot and smells of burning...

Passive Regeneration - occurs on long journeys when the exhaust temperature is high and the soot burns off naturally. For vehicles which unfortunately don't get this kind of use, Active Regeneration is needed.

Active Regeneration - occurs when the level of soot in the filter reaches around 45%. The ECU makes small adjustments to the fuel injection timing and increases the exhaust gas temperature. This increases the exhaust temperature which then initiates the regeneration process, burning away the soot trapped in the DPF.

How they work

The cDPF is used by Jaguar, Land Rover, Audi, BMW and Mercedes-Benz. It uses a coated catalyst type DPF, giving the advantage of lasting longer (around 150k miles) as there is no additive to help regeneration but the disadvantage is that it runs at a hotter temperature.

The particulate filter uses new filter technology based on a combined filter and oxidation catalytic converters to store and, when the conditions are right, destroy the particulates.

The exhaust gases pass through the filter leaving the particulates behind that are too big to pass through the filter’s pores. As the filter fills with particulates, the engine management will access this and carry out a regeneration of the particulate filter to stop it blocking.

The engine management monitors the volume of the particulate in the filter by measuring the pressure in a pipeline before and after the particulate filter.

As the exhaust gas flows through the filter and the amount of particulate increases, the pressure difference will increase. This will lead to a change in signal voltage from the pressure sensor. This signal is one of the parameters required before the regeneration of the filter can take place. The particulate filter has two types of regeneration: passive and active.

Passive regeneration

This requires no special intervention from the engine management and occurs during normal engine operation. It involves a slow conversion of the particulate matter into carbon dioxide, becoming active when the DPF temperature reaches 250˚C (482˚F) and a continuous vehicle speed of above 40 mph is maintained.

During passive regeneration, only a portion of the particulate is converted into carbon dioxide. This is due to the chemical reaction process which is only effective within the normal operating temperature range of 250 - 500˚C (482 - 932˚F). Above this temperature range the conversion rate of particulate into carbon dioxide is increased. Higher temperatures can only be achieved using the active regeneration process.

Active regeneration

This generally occurs every 450 miles (725km) – although this is dependent on how the vehicle is driven. For example, if a car is driven at low speed in urban traffic, active regeneration will occur more often than for motorway high speed driving when passive regeneration will occur. This is due to greater particulate build up at lower speed. The DPF control software incorporates a mileage trigger, used as a back-up for active regeneration should it not start because of filter pressure.

Active regeneration of the filter starts when the temperature is high enough to burn the particles. The filter temperature is increased by introducing post injection of fuel after normal operations have occurred. Depending on the filter temperature, the DPF software requests either one or two post injections of fuel.

The first post injection of fuel retards the combustion inside the cylinder which increases the temperature of the exhaust gas.

The second post injection of fuel is injected late in the power stroke cycle. The fuel partly combusts in the cylinder but some un-burnt fuel also passes into the exhaust where it creates an exothermic event in the filter, further raising the diesel particulate filter temperature.

The active regeneration process takes around 20 minutes to complete. The first phase increases the filter temperature to 500˚C while the second phase increases it to 600˚C – the optimum particle combustion temperature. Temperature is maintained for 15-20 minutes to ensure complete incineration of the particles within the filter.

The regeneration temperature of the filter is monitored by the DPF software to maintain the optimum temperature and to ensure the temperature does not exceed the operational limits of the turbocharger. If the regeneration process can’t take place due to vehicle usage or driving style, certain diagnostic equipment such as Autologic can force a regeneration to take place.

The ‘forced’ regeneration process

To force a regeneration to take place using the Autologic select “DPF FUNCTIONS” and then select “DIESEL PARTICULATE FILTER REGENERATION”. After this option has been chosen, on screen instructions are displayed for the technician to follow with the procedure usually taking around 30 minutes to complete.

That makes sense as I've not done any great miles lately...best I drive it like I stole it then

Thanks Gaz

you don't have to thrash it, but just a 20 min drive at 70mph should do it.

I was joking

we found you need to be over 50mph for the whole 20min period otherwise it wont complete the cycle - so a good long road is useful

or get the DPF dongle! Cheers

James