I accessed the bolt from the top but you do have to get underneath to determine where the cable is attached to the intake manifold and release the cable from these clips. I believe I did remove the oil filter to be able to see the attachment bolt but you can determine that as you go. A very bright flashlight will help you locate the bolt. IIRC it takes a 5mm allen socket, universal joint with a very long extension. Be sure to gunk the area well before removal---very greasy---and to clean out the allen head so you don't strip the the head and create a real nightmare Let us know how it goes. Mark