I got as far as trying to load a later DVD system map onto a Firewire-capable drive that I purchased using the Denso program that the SDD function invokes, but the map file format on the later maps was incompatible with the program.
The vehicle is now owned by a son who has no intention of trying to update the maps. L405 D350 SE Carpathian Grey D5 19" rims

I am looking at chopping off the 4 pin connector in the glove box, possibly the folder format on the later USB sticks that JLR send out for map updates could be copied over to a 1394 firewire hard drive, it would still need the NavTeq password ( which I believe the VIN of your car is needed to create the password ) , the Denso unit in our cars prompts you to enter the password ( numbers onyl) , does anyone know how many numbers the later USB stick maps use on L405 cars ??

The DVD that the Denso conversion program failed to successfully read when I was hoping to create files on the Firewire drive was for a MY16 D4 IIRC. Whilst the Denso program happily formatted the drive, the DVD file format was incompatible which caused the conversion program to abort.

Edit: The connector doesn't provide direct access to the internal HDD, only as an input to the function that reads map data from the FW drive to load the map onto the HDD. L405 D350 SE Carpathian Grey D5 19" rims

yes, John said in his first post that "The processor within these units is a Renesas UPD35003MNA. This is an embedded device designed for vehicle applications, has triple Arm Cortex cores, and multiple embedded interfaces"

So the 4 pins in the glovebox may use the Fireware protocol to transmit data to the Denso unit (after the correct NavTeq password has been entered, as per the Denso menus that the Main Dealer follows to update to latest maps, and then the Denso unit saves it on the Hitachi 40GB drive ( which is more than likely an IDE connection to the Denso motherboard ( just a small PCB )

hmm interesting RR 2005 4.4 petrol
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Previous MG J2, CITROEN light 15 x 2 gone unfortunately
Present MERC 180e, RANGE ROVER L322, JAGUAR XJS, MERC 280SE, MG F, JAGUAR S-Type 6v 2003, jaguar s-type 8v 2004, Ford Cougar