Had same with my 15 plate diesel - and it is a feature of the clogged DPF. Just before the DPF is egr and a temp Sensor in the box b4 DPF.. Check this sensor first. Presume you also get the booming exhaust whilst DPF is cleaning (egr active) ? Would advise keep checking oil level too- dilution can continue even when you don’t notice smoke- next to go is serious stuff- oil gets into the turbo…not good and £££.
definitely a DPF issue - dealer based forced cleaning (fire ext handy) might solve short term. Other issue I found was a crack in the split exhaust manifold, which suggests air getting into DPF, creating soot and ash deposits- oil burning in DPF doesn’t then clean these deposits, so cleaning cycle repeats…even if system alarms thinks all is good..
Ended up changing the lot- DPF, egr, sensors- ran fine with no smoke for 50k further miles.. add a dealer supplied DPF cleaner fluid every 6 months..they work.
incidentally, whilst mine was in for repairs, 4 others were too with same issue- there was a suggestion of biofuel / bad fuel batch. Not convinced.
