No worries Dan - We carried out the same check on the XJ which I sold a couple fo years ago, I built a lift for it and fitted 235's. It had no OBD so it was the GPS and the speedo too. I did not bother with the Range Rover, it was academic being a V8
I found this which is of some use
http://www.4wdaction.com.au/forum/viewt ... 25&t=66278 - will keep digging for information.