I came out this morning and started the car - instead of firing right up, it went off of the starter and was sluggish starting. Once fired up, I noticed the poer steering wasn't working, then looked at the dash and the tach wasn't working, the IMA battery charge was showing empty, the 12V battery light was on, and the ABS light was on. I stopped, revved the engine and the tach came on and the IMA battery charge returned to about 80% (where it was the previous day). I can't remember if the 12V and ABS lights went off. I then pulled out and drove off because I was late for work. As I was driving off, the power steering was cutting in and out so I turned it around and parked again then took another car to work.
I've been throwing P1449 and P1600 for a year or so, but this doesn't seem related to me based on previous experience.

Where should I start? I'm leaning towards a sensor of some sort (maybe on the 144V battery?) but I don't understand why the tach wouldn't work.

For some background, I am very experienced with cars, plus an electronics technician, but I don't even know where to start with this. Any suggestions are very welcome.

 

UPDATE: The 12V battery was just really, really, low. I put it on my 12V charger for 30 minutes, and it fired up and everything was working as normal.
Before that I drove it around for about 10 minutes and it never charged up enough to work properly. The IMA batter ynever charged or discharged, the radio didn;t work, and the dash shut off when I turned on the A/C. Afterward the charge, it started on the 12V starter, then everything was back to normal. The IMA battery showed completely empty, but went into a positive recal once I started driving it.
The only thing I can come up with is that the 12V system was so low that it wouldn't engage the charger to charge up the 12V battery. So I guess this just goes to show that the first thing you should check when weird stuff happens is the 12V battery!