Since many of the circuits through the ECM are very sensitive to changes in voltage or resistance, down to the hundredth of a volt or ohm, and since dielectric grease is an insulator, I don't recommend using it on the ECM connector or any other module or sensor connectors in a Jaguar (or BMW, Mercedes, Porsche, etc.). Better to make it part of your regular oil change maintenance to clean the leaves and seeds out of the ECM area and clean the drain so it flows water freely.

Last year I resolved some weird transmission shift issues on an X350 by cleaning out the dielectric grease that a transmission shop had put in the Mechatronic electrical connector. I've solved electrical gremlins on other cars by cleaning dielectric grease out of connectors, so I personally recommend that you never use it on module or sensor connectors.

Cheers,

Don