You didn't say if you hooked the ground direct to the battery also. Remember if you do; to be sure and fuse the lead though. If you didn't, a bad ground path can also cause voltage variations that the T2 is unable to handle.

It can also be an internal short or open in the vehicle battery. Intermittently bad battery can start and run a vehicle OK, but absolutely give computerized accessories fits or even destroy them. If you have one of those sealed cell jumpstart packs, I'd try running the EZ off that for a couple hours, to eliminate doubt about the quality of the electricity that the vehicle is making.