Exact same problem with mine a couple of months ago.
I agree that it's probably the pilot wire. We had a short period of intermittent function including a couple of very incriminating instances where nudging the charge cable on the ground caused it to kick in. Then it finally failed for good.
When I took the cover off my unit I noticed that the cable had pulled some of the way through the strain relief, and the bullet connector for the pilot wire was actually disconnected! BINGO I thought. No joy, it still didn't work when I hooked the connector back up. Which was consistent with the fact that for a while it was actually flaky when moving the cable itself far away from that junction but still worked sometimes. I had a flaky connection within the cable and the connector coming apart just made it a permanent failure, not directly related.
Anyway...you can easily check the continuity of the pilot wire once you get the cover off the unit. The blink end terminates in a junction block (might need a fairly thin probe or wire to get the J1772 end).
Solution was to buy a new Leviton cable off of Amazon ($170 or so) and wire it in. The crimps at the Blink end were not something I could reproduce easily so I used wire nuts at that end, repurposing the last few inches of each wire from the original cable so the crimps would be solidly in place in the screw terminals. Other than that hack, which I hope won't burn down my house, it works great now.
As noted in the thread I followed from someone else who did the same thing, the Leviton cable is slightly larger than the original, so the strain relief pieces are a very tight fit. I had to dremel out one piece, and remove a rubber gasket to get it all to fit back together, but now it's nice and snug.
Here's the thread which I followed, and the link to the replacement cable:
http://www.mynissanleaf.com/viewtopic.p ... 7&start=20
http://www.amazon.com/Leviton-A2034-PEV ... B00FH7EVN8