Question

I have the engine code P1421 on my 2008 Nissan Versa, check engine soon lite don't get off

Answer 1

If you have no drivability problem, you may have to reprogram the ECM. There is a service bulletin for that problem that recommends reprogramming the ECM. Unfortunately, only the dealer can do that for you. See "Tech Notes" on the code page for bulletin information.

P1421 Nissan - Cold Start Control
Read more: https://www.autocodes.com/p1421_nissan.html