Can I e-file when I have a W-2c?

Yes you can, if you have not completed your tax return you can enter the W-2c like you would a regular W-2. To enter the W-2 in TurboTax Online:

1. Sign into your online account
2. Click the orange button that says "Take me to my return"
3. Go to Federal Taxes then Wages & Income
4. Scroll down to Wages and Salaries and select Start/Revisit
5. Enter the W-2c
6. When you reach the screen that asks "Do any of these uncommon situations apply, check the box for corrected W-2
7. Be sure to delete the first W-2 if it was entered.

If you have already filed your tax return you would first need to wait and see if the return is accepted or rejected. If rejected, you can go back and add the Form. If accepted, you would need to wait until after you have received your tax return and then Amend using Amendment Form 1040X. Here's more on Amending :How to Amend my 2016 tax return