This is the condition caused by a Forced Regeneration for a Diesel Particulate Filter (DPF). This smoke is produced when a DPF Forced Regen attempts to “clean” the DPF by injecting raw diesel fuel into the exhaust via the factory fuel injectors. This fuel burns in the exhaust and heats up the DPF to around 600 Deg Cel. At this temp the DPF cooks off most of the Particulate Matter. This process is NEVER completed to a level that cleans the DPF completely. In fact, probably only 30% of the DPF is cleaned. Sooner or later the DPF will fill up and regens will be less and less effective.