----------------- 9/30/16 UPDATE -----------------
Checked with a scanner - No Codes.

Engine battery terminals looked corroded. Measured voltage 11.2 volts. It may be the original battery too.

Put the battery on my desulfinator and will check it tomorrow. It looks like my Miata battery might fit in there for a test at least. But for now, my bet is the battery is too low to properly drive the sensors or the computer.

Your thoughts are welcome. Thx

 

This is a good question.

What I would do first is check the oil. If it needs to be replaced, do it immediately.

Next, I would check the levels of electrolytes in the cells of the battery. In order to do this, take off the cell caps, shine a flashlight into each of the cells and inspect the level in each one. The level of distilled water and electrolytes should be equal among all the of the cells. If a cell is low, then add distilled (and only distilled) water to the cell and be sure that the electrolyte covers the plates of the cells.

If the levels in the cells are equal, then what I would do next is check to see if the battery has enough voltage, which should be 12-12.6 volts. If it's between 12 and 12.4 volts, then slow charge it and check the voltage again in about 45 minutes to an hour. If it has 11.7 volts or less, it is discharged has to be replaced.

 

Maybe a dying cell in the power pack, or, more likely, the standard 12v battery making the computer go wacky?

Weak 12volt battery will do this that's the first thing you should check, if the battery is old just replace it.

 

Well, the good question is, why a fine vehicle is neglected on maintenance.

Threshold voltage for 12V battery is 11.7. Considering that if it's still original battery, likely Panasonic, definitely deep cycle, it's 11 years old and a miracle it's still holding, especially with corroded terminals.
Please, start with replacing 12V battery. Again, it's a deep cycle battery, not regular cranking one. Do your car a favor, do NOT stick a regular acid battery in there. I replaced mine with Yellowtop Optima, but you may find other options.
Then do 3 consecutive Start/Shut down cycles and goof lights should go away.
Of course, please, clean terminlas and lubricate them with dielectric grease before reinstall.

 

So the 12V battery took a charge just fine. I used the BatteryMinder which I think is only about 1.5A max charging rate (extremely low) and it brought it up to 13.5V before kicking into desulfinator mode.

All the dash lights went away immediately with the battery charged, as did the funky behavior with the door locks and window switches.

I made a 30 minute trip just fine, but the lights came back on and the switches stopped working properly after starting to go home.

After resting overnight, the battery is reading only 12.29V (normal should be 12.6V / 6 cells x2.1 volt each). This isn't low enough to indicate a bad cell, so my guess is the alternator may be bad.

I seem to recall from my wife's Prius that you have to jumper two of the pins somewhere so you can override the computer, bring the engine RPM up above 2500 or 3500 and get a voltage reading.

Can anybody tell me where to look for the alternator test on one of these hybrids? Thanks!

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UPDATE: Just started the vehicle, waited until the engine fired up and the voltage picked up to 14.0V at the battery terminals - and that's without trying to raise the engine RPMs. Conclusion: The 12V battery is toast. Ordering a new one tonight.

It does still seem strange that the little trickle charger was able to charge it if it were truly bad, but it's only a $100 to replace and I don't have time to fool with it.