Welcome to TBN, stymey. Don't own a JD344J loader... would definitely be a welcome addition to my shop, though!
Often, there are various error codes listed in your Owner's manual or the Maintainence manual. I'd have a look see in the back of those.
Next, I'd get on the phone and ask the local JD shop foreman for his diagnosis.
You didn't mention whether there were any problems with your loader's operation... I'm guessing you're still using the loader, correct?
AKfish