The following is lifted from more than one Service Bulletin available to Dealers on the subject of DPF, but it's clear from some posts that some staff are not fully aware of these and/or are not passing relevant infomation onto customers. There's much more data than this but a lot of it is not necessary for a general understanding of the system and what to expect during it's operation.
Regeneration will usually occur every 800-1000km but may be as regular as 400km under certain conditions. During regeneration you may notice a higher than usual idle speed, operation of the cooling fan, slight increase in smoke emissions, and high exhaust temps- these are not to be interpreted as 'faults'.
The lifespan of the DPF is typically 250,000km though this can be reduced by driving style/oil consumption/engine faults etc.
Operation of the DPF lamp
does not indicate faulty operation of the vehicle. The lamp comes on to indicate to the driver that the DPF requires time to regenerate and that the engine should continue to be run during this time, after which the lamp will go out. The ideal conditions for natural regeneration are a speed higher than 60km/h at about 1800rpm and will take approx. 10mins, although the chances of maintaining this will obviously depend on road conditions- as long as the engine continues to run, the DPF will perform its cycle. Interrupting the procedure by switching the engine off will cause the DPF lamp to remain on.
Regeneration can be carried out with the vehicle stationary although the amount of fuel needed to keep the exhaust temps high means that regeneration will be stopped after 3.5 minutes to prevent excessive oil dilution.
If the EFI ECU is interrupted it will attempt regeneration upto 6 times before it decides the only course of action is a forced regen by the Dealer and to indicate this it illuminates the EFI (MIL) lamp.
When this occurs the Dealer will need to check various parameters are within range (including checking cam profiles, injector shims, thermostat opening, oil level etc) then perform a forced regeneration- if the filter clears ok, then the vehicle is returned to the customer. If however the blockage is unable to be cleared to a satisfactory level despite all other components operating within spec, and Fiat Technical agree, then it will be necessary to replace the DPF.
Hope this helps.