I left all my original wiring in place. I made an extention from a piece of old harness I got with a ecm and used used audio connector from a olds radio for the end that hooks to the original wiring. When your finished just unplug it and your'e good to go. No need to change any loomed cable. Mine sit on the trans tunnel and slides under the seat. Been two years and no problems. I do the ocd. This is for a 7427/6395 pcm.