runaway rpm,s

After sucessful 4kwh install I was coming off interstate at 65 mph avg. when red light began to show on phev switch. Of a sudden the ice reved to 3700 rpm and loss of power. I was only able to get up to 25mph after red light.the ice contined to rev and of course the dash lit up like a christmas tree. I got to top of hill and pulled over and shut it down. I started it up and every thing worked fine except the red triange and check engine light were still on and all the other lights were off. I pulled into Bachman
Toyota about five miles further and their tech said this:
"There is a code poa92 detail 606//adv there is a cust.modified addtional battery,in which we cannot svc." He cleared the code and I drove it home a total of about 60 miles and it is fine. What went on ? has any one had this experience?