Athearn MP15 HO Scale locomotive. HO scale.
Remove the couplers and then lift off the shell.
Whether you use the DP2X or the T1 the jumper plug that attaches to the 9 pin JST must be removed.
Photo below show a DP2X installed, this is a very easy, plug 'n' play installation. NOTE: Jumper plug is removed from 9 pin JST connector.
Photo below shows T1 decoder installed which is a very easy installation.