Here's the problem- you have a recent (last3 years cataloged date) Lionel engine. Lionel has not posted diagrams for these engines, and given recent discussions and changes, your best bet is to go through Lionel support. https://www.lionelsupport.com/contact-us
Again per the support page for your engine, NO PARTS ARE LISTED.
https://www.lionelsupport.com/...-Train-Master-6301_2
Something to consider when folks keep saying Lionel is doing great, buy Lionel because they have the parts and service, buy Lionel because "Lionel".
Except that again, there is a multi-page discussion about how they removed a massive swath of the electronic parts prior to the sale this weekend. They removed ALL LCP2 boards- which might be what your engine uses- some time in the last year after I documented how to use them and how they were wired.
They (Lionel) want dealers and YOU the customer to ONLY go through them for support.
http://www.lionel.com/articles...ranty-Repairs-Notice