Talk to the 401K plan administrators to see what your options are  however the you usually have 60 days to repay the loan in full and if you don't then the unpaid balance  it is considered a distribution from the 401K and they will take the amount owed from the retirement account AND  issue a 1099-R  which is not only taxed at your ordinary tax rate  but subject to a 10% penalty if you don't have an exception.