2009 Prius won't turn on, jumpstarts from 12v but doesn't stay on or go to 'Ready' mode

Hi Arturia, You will get a lot of advice on your problems and potential problems here. Some of it will be very technical. And some of it will be contradictory. Replacing your hybrid battery will likely be quite costly. Can you afford, and do you want to do that?

Disconnecting your present 12 v battery and attaching to the positive and negative leads (not fully installing in the well in the back)) almost ANY other fully charged 12v battery might give you some further information. Do not be concerned about the fuel gauge at this time. When you disconnect the 12v bat, and connect a fully charged battery, various devices have to sense this. It will likely require that after you attach the new 12v battery you have to do the full start sequence twice. After that you might also have to hold the power/start button for a while (30 seconds+) to get the car ICE (gas) engine to start. You might then not have any warning lights because disconnecting the 12V battery "resets" some/all of those lights. If you get to this point,. the ICE engine starts, the Ready light should come on. There are a few other possibilities but this will be a start.

If you want details on how to do any of the above, just say so.

If you are going to continue with your appointment to change the 12 V and hybrid battery you might want to get a firm quote for this job before it begins. As you suspect this might or might not solve your problem. Other potential issues include the inverter and the inverter cooling system. I'm presently "running" 2, sometimes 3, of my Priuses with some/all of these problems and have been doing so for a few years ;-) It's the exact opposite of reliable transportation, but it gets me where I need to go if I take known steps. Good luck.

 

guessing at what might be wrong can be unnecessarily expensive.

how many miles on your car? how old is the 12v?

you should get the 12v tested, and have it charged or replaced if needed.

if there isn't a hybrid mech in the area, you should tow it to a dealer for evaluation. the service manual will help them determine the problem.

 

If the hybrid battery needs to be replaced, it will throw (among other things) a P0A80 code.

The first order of business is to get the codes read by a reader that can talk to all 20-some-odd computers in the Prius. There are several bluetooth OBDII dongles that you can connect to the car to talk to various apps on your phone. There are countless threads here about those, so I won't try to summarize. That's cheaper than having it towed to a dealer and you can read the codes over and over.

But if you replace the hybrid battery and find that it didn't fix anything, you'll have wasted a ton of money.

In fact, before you even bother with a code reader, check the AM2 fuse. It seems most likely to me that the inverter coolant pump seized up and blew the AM 2 fuse. If you disconnect the plug to the pump, you can replace the AM2 fuse with a spare and drive the car slowly and not very far. (You don't want to overheat the inverter!) The pump is something like $140, IIRC, and not terribly hard to replace. Here's a link to a picture of the plug provided by one of our most knowledgeable members.
Possibly inverter coolant pump? | PriusChat

 

Yes, it makes sense. You can get a small lithium rechargeable emergency jump start battery from Costco for about $60. You can attach that to the positive jump start lug in the fuse box under the hood, and the negative to bare metal somewhere (be careful with polarity). That should give you enough power to open the trunk.

Otherwise you can get into the back seat area, fold down the backs of the back seats, take off the "trunk plastic cover" and crawl back to the trunk latch. With some effort, and maybe a screwdriver and flashlight, you can push/pull the latch and "pop" the trunk. Good luck. Glad you have a positive attitude.

 

There's probably a spare fuse in the fuse box. Just be sure to unplug the pump before you replace the fuse.

Your 12V might be dead now, but the car didn't stop on the highway due to a dead 12V. Unlike a gasser, once the Prius is running, you can disconnect the 12V and it'll keep on running. So my money would be on a bad inverter coolant pump along with a possiblly dead 12V.

 

Maybe even a gasser will keep running? Not sure about that.

 

Probably will keep running, but not a good idea in a conventional car with an alternator.

Those alternators are belt-driven from the engine, so the RPM they run at is changing all the time, and their voltage regulation is often a coarse three-level deal that depends on the battery being connected, acting kind of as a big surge tank to smooth out the voltage swings. Some of the more sensitive electronics in the conventional car might not survive running around with the battery unhooked.

The DC/DC converter in the Prius doesn't depend on engine RPM (or even whether the engine is running), and its regulated output barely even wiggles when you unhook the battery.

 

Possibly, but definitely not always. A friend just had a battery die in her Dodge Journey due to an alternator failure. It stopped dead on the way to a shop to get it fixed. She wound up calling a tow truck.

 

That's a special case. If you disconnect a Prius's battery while its DC/DC converter isn't working, that Prius will go dark just as fast as a gasser with a failed alternator.

 

Totally agree.

 

Certainly. I thought you'd already done that. But I never recommend using regular jumper cable on a Prius. Getting them backwards can be mighty expensive compared to buying a lithium jump battery. They have polarity protection and you can use them to jump other cars, which is a no-no to do from a Prius.

That looks right. But the cheap aftermarket ones have a reputation of not lasting long. OEM is your best bet, if it turns out that the pump is bad.

 

did you disconnect the bad inverter pump before jumping as jerry suggested?

 

IF the 12V battery is really that discharged, then it has to be charged for many hours with the correct equipment (ie, a "smart" charger that can handle AGM batteries) - that's assuming that the battery is any good at all.

Posted via the PriusChat mobile app.

 

Sounds like a very low 12V. As @mr_guy_mann said, it'll take more than that to get it charged back up, assuming it will even take and hold a charge. And, if it's low enough, a smart charger may assume it's a 6V battery and not even try to charge it.