My dealer was clueless on how to test this. They checked for ECU error codes (none of course), plugged it into their AV charger, gave it a full charge, and called it a day.
Even the 2 Nissan techs who came to my house were no help. They were just "gathering data" to feed up the line, but even though they said this was given a high priority, and many people upstairs were involved, I haven't heard back in 3 weeks. Their only suggestion was to let me borrow an AV charger. :x I turned it down, because I would have needed to rewire for a huge 50 amp 240 connector that cost >$60.
I gave them plenty of info to go on: we had tons of rain, I drove through some deep puddles, I showed them the high leak current on my meter, and they still haven't bothered to actually physically remove a panel, check a connector, or look for water intrusion. I've resolved to fixing it myself when I have more time in April/May. In the meantime, the leakage current is low enough that my modified factory EVSE works fine. The highest leakage I have seen (while the techs were here no less) was 19ma, and the factory EVSE is supposed to fault at 20ma. They simply see that problem as being my Schneider EVLink, which faults at only 5ma. If it turns out to NOT be water intrusion, I suspect a problem with the charger in the car itself, some leaky component. But, given that the leakage current seems to vary greatly, some days as low as 5.x ma, I'm pretty sure its water that has gotten past a seal somewhere. My biggest worry is that this longterm oxidation of some connector or components could cause permanent damage, giving me reliability issues in the future.
BTW, Schneider says typical LEAF current leakage is 1-2ma, which I verified on 2 other LEAFs, a 2011 demo and a new 2012. Testing is relatively simple, if you have a friend who is an electrician, and he has an AC milliammeter. You just disconnect the ground wire between the EVSE and your breaker panel, and put the AC ammeter between the break so it reads how much current is going to ground.
Does anyone know of a device to test 240 volt ground current? I see they make tons of household 120 volt testers, but is there anything off the shelf to test 240? Every Nissan shop should have one, IMO, but with all the different 240 connectors it has to be a tough product to find.