occasionally blowing white smoke from the exhaust
That sounds like condensation due to the cold weather and maybe some short trips where the engine does not get warm enough to dry out the exhaust system.
Joe. The OP didn’t specify the year. Maybe a DPF problem?
Tester
It could be several problems and I fear I don’t know Chevy diesels well enough to go there, which is why I worded my reply the way I did. 