2007 - "Cannot Change to EV Mode Now"

I have a 2007 base model and for the last two months I keep getting three beeps and on the mfd shows up "Cannot Change to EV Mode Now". I haven't done any mods to the car. It seems to happen during the first couple of miles after start up, but it also happens when I need a little extra power to pass a car on the highway or if I've been coasting for a few seconds and then hit the accelerator again. I live in Atlanta and the temps have been 60-80 degrees for the last few months, so it's not getting to hot / cold.

This might be a coincidence, but it seemed to have started doing this after my last emissions test. The gentleman who did the test acted like he had never seen a prius before and took him a good 10 minutes to hook up his equipment. As this is going on, he proceeds to touch all kind of buttons on the MFD and got to screens I have never seen before. It wasn't until a younger co-worker came over and showed him how to hook it up that he stopped messing with buttons. My question is, could he have done anything on the screen that would cause the issues I'm having.

I've checked my 12v battery (saw the Youtube video) and the numbers seem to be in line with what the standard is, I think. Here are the readings below
no acc - 12.1v
acc - 11.8v
acc w/ lights on - 11.4
with full power on - 14.2v
It's probably time to change the battery anyway, but do you think it's what is causing the problem.

Sorry for being so long-winded, I just wanted to give out all the details I could. Thanks in advance for any help.
Adam

 

I bought the car used in 2009 and have done any kind of modifications (EV Mode Button). Unless the previous owner did it and hid the button...but I don't see anything like that. The only other thing that has been giving me a problem is the AC/Fan behind the glove compartment doesn't engage all the time. I have a replacement, yet haven't switched it out yet. Could that have anything to do with it?

 

Thanks bisco for the tip. I bought the car used from a Toyota dealer, so I didn't have any contact with the previous owner. I just took the glove compartment off and it looks like there is a mod chip installed. I attached a photo to look at...does anyone know which company made this mod and maybe a link to instructions on how to use it.

 

Thanks everyone for the help, I removed the EV chip and everything is back to normal.