If your puppy urinates or defecates when left alone, this may be messy but perfectly normal. If you're leaving your pup alone too long (crated or not) or you leave him uncrated you can expect young pups to go. This would be similar to an infant without a diaper on - hardly a surprise when there's a mess, yes?
Resolving this is making sure your pup gets outside enough or is set up to go in a puppy-proofed room if you most leave him for long periods (never ideal).
That you have a good schedule when you are home and get him out regularly. Then, as he matures, everything should fall into place.
BUT - if your normally housebroken dog urinates or defecates in the house when you leave him alone? This is a sign of separation anxiety or upset or a health issue. Anytime an adult dog develops a new unwanted behavior, please get to your vet before you get upset. This could well he a health problem. Next, has your dog been upset? Is their construction on the street, is a neighbor harassing your dog (happens from time to time) or maybe the meter reader came that day? Upset dogs can show their stress by going to the bathroom. If it is random or related to some change, try putting him back on a crating schedule, as if he were a pup again. This can help get a dog back on track.
If this is happening consistently then it may be the stress of being left alone stimulates him to go. Because it is your leaving that triggers it, he will make a mistake within minutes of your leaving. If that is happening then please... speak to your veterinarian as medication may help your dog get over this anxiety. Read and apply "Separation Anxiety", “Six Steps to a Better Behaved Dog” and “You’re Grounded”. Do NOT get upset with your dog for his mistakes, tat will only make his anxiety about being alone worse! Once he is calmer about being left alone, the mistakes will probably stop.