This is what was on a Jag Forum:
P1797 : CAN network to gearbox. CAN stands for controller area network - basically an electronic signalling systems.
First move is to fully charge your battery or preferably replace with a known good one and check the battery connections. Then work through all the gearbox electronic connections with contact cleaner and easing them in and out. Your fault may be no more than a poor connection. If that does not work you need someone competent with electronic diagnostics and probably Jag main dealer diagnostics.
P1797 : CAN network to gearbox. CAN stands for controller area network - basically an electronic signalling systems.
First move is to fully charge your battery or preferably replace with a known good one and check the battery connections. Then work through all the gearbox electronic connections with contact cleaner and easing them in and out. Your fault may be no more than a poor connection. If that does not work you need someone competent with electronic diagnostics and probably Jag main dealer diagnostics.