what is cost of a smoke test for check engine light code P0456 to find emissions issue?

What is your question?

check engine light came on; replaced gas cap; cleared code; 2 months later, check engine light came on again - same code P0456; will a smoke test indicate where (if any) there is a leak? 2012 jeep libert

How long has your 2012 Jeep Liberty had this problem?

2 weeks