I made an excess roth contribution in 2017 and received a 1099R in 2018. How do I amend 2017 return? Can't find a PJ code in 2017 entries for 1099R.

I believe its too late for 2017. I believe you get charged interest on the excess Roth contribution. I would suggest contacting the Financial institution that you made the excess Roth contribution. They may be able to save you the interest charge and correct the excess roth contribution.

There are 2 entries for box 7, put the "P" in 7a and the "J" in 7b.