I found this in the Focus RS forum. The TC has a painted ground connection like the Focus. I removed the paint with a sanding wheel on a Dremel to improve the connection. I used a jumper cable to maintain the ground connection during the procedure so none of the vehicle's memory would be lost.   https://www.focusrs.org/threads/how-well-are-we-electrically-grounded.115556/   I will add some corrosion inhibitor later but it's not essential here in dry California.   Al