I have a 2014 Prius with an intermittent no start. I'll unlock the car with the fob, get in the driver seat, press the brake pedal, press the start button, the dash will light up but the speedo and the "ready" light don't come on. I then turn the car fully off, try again, sometimes it works, sometimes it doesn't. Some times it takes 3 or 4 times of doing that, and sometimes even getting out of the car and locking it and then unlocking it and trying it all again to get it to start. But it always does start eventually. Brake lights do come on so that tells me the brake switch works. The problem occurs with both key fobs, one that actually has a new battery in it. Once started it'll run and drive no problem until I get to the destination. I'll turn it off and it'll turn right back on again. The no-start only sometimes pops up after it sits for a few hours. Any ideas?
It might be your actual 12v battery getting close to its end of life. If not, try resetting your ECU by disconnecting the 12v for a few hours and reconnecting. See if that fixes your issue.
Actually, that reminds me....I replaced the 12v battery before I took it on a road trip back at the beginning of the summer. It was an O'reilly's brand battery. I guess it could be a lemon going bad already? I'll load test it tomorrow. Does a weak batt just not have the juice to flip the HV batt solenoid so it just sits in auxiliary mode?
I'm 99% sure they're tight, I'll double check them and give them a wiggle tomorrow when I'm load testing it.
Did you charge the battery? Those places don't keep them charged. So it's been sitting on the shelve for a year probably. A weak battery causes a lot of problems. You didn't say how long the drive is but it's probably not enough to charge the battery. It's likely it's just enough so you can restart it after a short time, but not enough to keep the voltage high enough after several hours. You should charge the battery overnight, or at least several hours.
Even if the battery didn't come topped off, how could it lose all it's charge after a few months? These cars don't draw a lot of current to start the engine like an ICE does. After it flips the solenoid for the HV battery pack, it's just hanging out getting charged up, isn't it? The long road trip this summer was 1500 miles 1 way. I'm sure the battery was charged to it's fullest during that drive.
SOLVED - It was a bad 12v battery. I tested it and it came out to 10v and 220 CCA. It's a Super Start Platinum brand battery, manufacture date of 7/22. I'll be taking it into the store tomorrow to see if I can get it exchanged.
Make sure to get it covered by warranty. Tell em it left u stranded multiple times and had to get jumped by roadside.