A loan is never taxable as long as you pay it back.
401(k) loans are required by law to be repaid by payroll deduction. These deductions are not new contributions (although you might make new contributions at the same time).
If you separate from the company, you have 60 days to repay the entire loan balance. Any part not repaid is taxable income to you, and may also be subject to an early withdrawal penalty. If you can't repay the loan within 60 days, you also have the option of making a deposit to a private IRA or or the retirement plan at a new job and calling it a rollover of the loan funds rather than a new contribution. Then on your tax return you can report that you rolled over the funds instead of paying tax on a distribution.
But if you don't repay or rollover the loan, the money you keep is a taxable distribution, there are no exceptions for hardships.
