As a rule of thumb, white smoke from a diesel engine suggests the fuel is not burning properly. If your engine only blew smoke when you first started it up each morning, I’d suggest the glow-plugs weren’t working properly and heating up the combustion chambers to gain a complete burn of the fuel.
But since it’s blowing smoke all the time, I think you could be looking at a fuel-injection problem. The injectors themselves could be bad (and it only takes one dud to make gales of smoke) or the system is mis-timed and not injecting the fuel precisely when it should be. These engines self-analyse themselves as you drive and it seems the car knows it has a problem, because it has turned on the check-engine light as a warning to you that something is amiss. Your first move should be to have the injectors checked as well as the injection timing
