How to ground PDC?

This is a real tough one because we/I/ they have no idea what has changed as in "what all changed" from factory to "now." If you can, get access to an original OEM manual, which in a roundabout way, will show the factory ground points. These originally were specific. Not only for DC current, but for noise suppression. "It just might be" that you have created some sort of ground current/ ground loop that can/ has damaged some sensor(s)

I would not concentrate on the PDC. It is far more likely that some cut harness has changed or eliminated ground paths for something related to the CPU or related sensors

Really without painstakingly comparing what is "now" against original documents, there is no way to tell