After reading an article about On Board Diagnostics in 2013 Ron Wood decided to look into what is available.
For background Volkswagen introduced the first on-board computer system with scanning capability, in their fuel injected type 3 models in 1969. In 2001 the European Union made EOBD (European On Board Diagnostics), mandatory for all petrol vehicles sold in the European Union. (And Diesels since 2004). Although the OBD-II specification has been mandatory for all cars sold in the United States since 1996.
OBD systems give you access to state of health information for various vehicle sub-systems. The amount of diagnostic information available via OBD has varied widely since the introduction in the early 1980s of on-board vehicle computers, which made OBD possible. Early instances of OBD would simply illuminate a malfunction indicator light, or MIL, if a problem was detected—but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardized digital communications port to provide real-time data in addition to a standardized series of diagnostic trouble codes, or DTCs, which allow you to rapidly identify and remedy malfunctions within the vehicle.
A list of codes can be found here: http://en.wikipedia.org/wiki/Table_of_OBD-II_Codes
There are a number of ways you can connect to your OBD port ranging from simple cable connected code readers to Bluetooth and Wi-Fi apps for your PC, smart phone or iPad. I decided to go the Wi-Fi route to connect to my iPad and purchased a Wi-Fi ELM327* interface off Amazon for £8.
(* Warning: Pirate clones: The v1.0 version of the ELM327 did not implement copy protection, and the code was copied and widely sold in devices claiming to contain an ELM327 device. Numerous problems have been reported with Chinese clones, partially due to bugs inherent in the early code. Although these pirate clones may contain the ELM327 v1.0 code, they may falsely report the version number as the current version provided by the genuine ELM327, and in some cases report an as-yet non-existent version)
The Jaguar XK OBD connection can be found in the horizontal panel above the driver’s right leg.
I now needed an interface to view the information on my iPad. I downloaded a few simple, free ones to try out the connection but could not communicate with my iPad. I returned the ELM327 and received a replacement within the week. This one connected immediately. I now needed a better app!!
I eventually decided on DashCommand by Palmer Performance Engineering. DashCommand is a touch screen friendly software application that allows you to display, and create, virtual dashboards. There are also numerous styles of dashboard available to download.