It's over fueling.
White smoke is unburnt diesel.
As it's repeating this at set intervals it could be it's over fueling to perform a DPF regeneration, and that process is failing
So the extra fuel it injects to ignite in the DPF is findings it's way out the exhaust as fuel vapour.
Now comes the bad news.
This unburnt fuel will find it's way past the piston rings and contaminate the engine oil.
If it's been doing it for a while you may notice the oil level start to rise on the dipstick and the oil stink of diesel.
This contaminated oil isn't good for the engine, but it can also get thrown out if it's way too high and the engine will "runaway", ie run on the stuff at full chat, with no way of stopping it until the motor goes bang in a big way! (diesels will run on anything oily)
A code read is a good place to start, but you'll more than likely pull faults caused by this AND perhaps the code for the fault it's self, they can all pile into each other and throw lots of red herrings.
I would check the oil and it's level and if it appears ok, take it to a diesel specialist, there are plenty around and they'll be best placed to test it, identify the problem and fix it.