the 1791 diagnostics code was disabled with subsequent releases. i can't remember which year it was disabled (2007?), but if it's anything like updating to the latest nav disc, i can only assume the nav system software update that's initiated when you insert the newer disc is what disables 1791 for those (who like me were) on the original nav system software. i stayed on the original nav disc for years to maintain 1791, but last year i got the latest nav disc for free so i upgraded my GAP EAS tool to the IID tool so i could enable nav on the move.
http://www.rangerovers.net/forum/41-gap-diagnostic/
http://www.rangerovers.net/forum/41-gap-diagnostic/
