CEL, Red Triangle with !, intermittent VSC light, and code P0093

Only the first time I have used it on the Prius and I did not reset anything so hopefully no harm done. Both before and after using the code reader, the dash lights continued to function as previously described (red exclamation point and CEL constantly on with (!) and VSC lights off after letting the car sit for a long while only to have them return after driving the car for a few miles).

I just checked the "unloaded" voltage at the fuse box terminal and it was now 12.51V. I opened the driverside door, turned on the HIDs, driving lights, and held the brake pedal down until what I always figured was just the normal sound of the car pumping pressure into the brake lines stopped. The voltage was then 11.6V.

 

Sequence of events was as followed:

1) Yesterday, all four dash lights in image #1 turned on. None of those lights have never before come on since the car was first purchased brand new in 2009. No other CELs have ever been present on this car.

2) This morning, the red exclamation point and CEL were both lights were both still lit. I drove the car for a few miles only to see that the (!) and VSC light have come back on. I return home from my errand and read the code using my generic scan tool. I received P0093. Codes were not reset. I let the car sit for a couple hours before my next errand. The same thing happened where the red exclamation point and CEL were on but the (!) and VSC were not. After a few miles, all four lights were all on once again.

 

No repairs or modifications made to the car. Just routine maintenance with M1 5W-30, M1 extended oil filters, 6k mile tire rotations that coincided with oil changes, and engine air filter changes as required. Gas is from either Costco or Shell (both 87 octane) depending on which location is closer at the time I need to fill.

 

Unloaded voltage this morning was approximately 12.5V. Loaded voltage was approximately 11.7V.

Only the CEL, red "!" triangle, and red car icon with "!" (on the MFD) were on this morning. After my 41 mile one-way commute to work (0% highway), these three lights remained the ONLY lights (i.e. no VSC or (!) lights like before). The only difference in the way I drove the car this morning was that I tried to minimize the amount of regenerative braking. I used the "light-on-the gas" coasting technique any time I saw that the car was trying to charge the battery going down a hill. The hybrid drive battery level remained at around 75% full for the entire trip.

 

It's disheartening to know that it's potentially not as simple as a mere aux battery change. I was hoping that the signs would be more clearly pointed to something I could resolve myself.

Question...does the "red ! triangle" always turn on whenever the CEL appears?

 

Found my way to the diagnostics mode on the MFD and did a loaded and unloaded voltage test. This morning, it was 12.4V unloaded, 12.1V loaded, and 14.1V after start.

With the HIDs and driving lights on, the loaded voltage drops to 11.8V.