2008 Prius C1241 and C1242 - Won’t start or go into ready

I have a 2008 Prius that threw codes C1241 and C1242 and the skid control buzzer came on. Now it won’t start. It also has 12 volts to the jumper terminal but no power to the OBD port, the display isn’t lighting up, the door locks aren’t working with the button inside the car, but the headlights work, and the brake booster powers up.

I bought this car used but like new and I’ve put the majority of the 380k miles on it. I drive it about 900-1000 miles a week back and forth to work. In January I put a new 12V battery in it. Immediately after installing the new 12V battery, the display didn’t work, and it had never had an issue before. I disconnected the battery and the display worked again. Now at least once a week I have to do this procedure again. So last week when I disconnected the 12V battery then tried to restart it, it wouldn’t boot up the entire system. After several tries it finally worked. So then I left for work and after 45 minutes of driving, several lights lit up and the skid control buzzer started going off. I just happened to have my code reader computer with me and checked them on the fly. It was C1241 and C1242. I made it to work but the next morning my Prius wouldn’t start. It has 12 volts to the jumper terminal on the front but the door locks don’t work and the OBD port doesn’t have power. I’ve checked all the fuses and tested the ABS 1 and 2 relays and both are good. My next step is to test the skid control plug for power. Does anybody else have any suggestions?

 

The CM has been going out ever since I changed the 12V battery in January. I’ve driven plenty of miles with it off because I was in too much of a hurry to reset it. So I checked that first thing, it won’t switch out of park. And also the ICE doesn’t turn on, this time there’s a lot more to it than usual. I’m getting it out of our parking lot at work soon, and as soon as I do I’ll be able to work on it easier. So far I’ve checked loose connections, checked voltage at the battery and the fuse box under the hood, pulled all related fuses and ohmed them, and pulled the ABS 1 and 2 relays and checked resistance on those too. I’ll check the BCPS next since it’s easiest to get to and I already have everything out of that area so that I could check the battery. Then if that checks good I’ll move on to the skid control ECU.

 

Thanks for your help! I feel pretty comfortable that I can do a repair on the CM myself with the assistance from people on here. I’ll definitely work on that soon, it’s very annoying when it goes blank. Tomorrow morning I might get a chance to work on the other issue. I’ll see how that goes after working night shift. I’ll post updates when I have some.