Is this really unfixable?

Are you still using the 12 volt battery that came with the car?

In any car, after 4 years the battery is on borrowed time, but in a Prius you never hear the 12 battery start the car, the HV Battery does that. This means you may not have noticed that you have a nearly dead 12 Battery.

Since the 12 battery powers the computers, no computer tracks the 12 battery, so there will be no codes saying 12 volt battery dead.

 

I concur, 12v battery would produce those symptoms. However, it is strange it happened while READY. When in READY, the inverter is doing all the 12v powering. However, if the battery is toast, and was pulling way more then it should, it could overheat that part of the inverter and it would shut down, (i.e. the dash will light up like a christmas tree and all power accessories will be lost).

So I would replace the 12v first.

Also, I know you say 2005, but what kind of 2005? Was it is a 2005 built in 2004, or a 2005 built in late 2005? There is a TSB for 2004 models I believe that can cause stalling. The Hybrid ECU goes wanky and the car stalls as described. Everything is perfectly fine the next time it starts up even without waiting inbetween. The fix is a 5 minute firmware flash from the dealership.

 

Don't ask them to check the 12v battery. Replace it. It is way beyond it's normal life span.

 

I would agree that replacing the 12V with the OEM battery or an Optima yellow-top with an install kit (better and cheaper?) should be a first step.

They should be able to update the firmware to the latest version without there having been any problems. I would try to have that done.

My guess is that is all you'll need, but you won't really know until it "doesn't" happen again.

Sorry for your travails. Best of luck.

 

Here is a link to both Toyota and Optima batteries for sale online

http://priuschat.com/forums/gen-ii-...12v-battery-replacement-cost.html#post1353484

 

I don't understand how a 12 volt battery could go from failing and causing above symptoms while driving , to working fine the next day.

I would personally be checking for an intermittent/slowing inverter coolant pump.
Have you replaced the pump via the warranty work yet? If not , now would be a good time.

And keep us posted.

 

If the 12V battery has a cell with an intermittent short, that would explain why the battery might test OK one day, and another day load down the 12V bus so that all of the warning lights turn on and the car stops running. A dead 12V battery would also explain why no DTC was logged by the various ECUs - if 12V power is lost then the ECU memory will clear (this is true for all ECU except SRS and skid control.)

Hence I agree that the 12V battery should be replaced. It would be a waste of time and money to have it tested, just replace it.

While the car is at the dealer, ask for the service writer to check whether all relevant SSC (special service campaigns aka recall) have been applied, including SSC 50P which is the engine and hybrid vehicle ECU reflash.

After all this is done, if the problem repeats, hopefully the new 12V battery will contain sufficient power to keep the ECU memories alive so that DTC can be retrieved which will provide a clue as to your car's problems. Good luck.

 

Concur totally. I am in same boat as you with 90K on 2006.
Wife complained tonite about strange behavior (Prius that is).
Plan to order the Yellow top batt ASAP w/ install kit.

P.S.- Dealer said 12v battery checked out fine few months back
from what I read, deterioration faster in summer heat.
Power is lower in winter, but cold weather better on life.

 

You can put the MFD into Diagnostic Mode & check the 12v battery's voltage yourself.

 

Its been repeated in the forum many times, most dealers don't test the 12v battery correctly. A load test would need to be performed to determine many failure modes of this battery. A search of the forum will turn up many instances of dealers saying the 12v battery checks out and when its finally replaced all the screwy symptoms disappear. Unreliable 12 volts in this car can cause nearly any malfunction indication. The errors are determined by the computers which can't make the correct decisions about error conditions if their 12 volt power has a problem. Try measuring anything with a digital voltmeter with a faulty internal battery connection.

 

+1 on the inverter cooling pump and 12V battery. A 12V on its last legs could muster enough energy to make the car Ready, but fail quickly when the inverter cooling system fails and takes offline the DC-DC converter. The inverter cooling pump is a free replacement in the form of a special service campaign, because, as you have seen, it can cause a safety issue. Get a new 12V and inverter cooling pump, and the car should be good to go.

Note, the car make have appeared to be running when it failed, but it was not. The 12V battery has to have sufficient charge to power down all ECUs. It is definitely possible for it to be in a strange intermediate state where dash lights are on, but the primary ECUs are off. And, if the 12V has gone down far enough, then most ECUs lose whatever trouble codes were stored.

 

Twice now, OPs have mentioned a failed inverter pump. Was this a recall issue for 05 Prius? Replacing a 5-6 year old battery is initially a far easier solution before getting into inverters.

I'm very anxious, as the driver must be, to see how this resolves.

 

It is easy. Adapted (text in bold) from:
Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 - 10

1. [FONT=arial, helvetica]Do this test after you have driven the car for at least 30 minutes. This will give the battery a chance to be fully charged. Actually it takes longer to get fully charged and the test should be done after the car has been off for a few hours.
   [/FONT]
2. [FONT=arial, helvetica] Put the transmission in Park. [/FONT]
3. [FONT=arial, helvetica] Engage the parking brake [/FONT]
4. [FONT=arial, helvetica] Push in the power button without pressing the brake [/FONT]
5. [FONT=arial, helvetica] Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times. [/FONT]
6. [FONT=arial, helvetica] Push on Menu in upper right of display screen. [/FONT]
7. [FONT=arial, helvetica] Push on Display Check [/FONT]
8. [FONT=arial, helvetica] Push on Vehicle Signal Check [/FONT]
9. [FONT=arial, helvetica] You will see the 12 volt voltage displayed. In accessory mode the voltage should be 12.6 [/FONT]
10. [FONT=arial, helvetica] With no electrical accessories on including lights the voltage should be fluctuate between 12.6 and 11.9. The lower the voltage, the less of a charge your battery currently has. If the voltage is low do not proceed as the load test might totally discharge your battery. (If you see a voltage around 13.8 you are seeing voltage from the high voltage battery being converted to around 13.8 in an attempt to recharge your battery. This normally does not occur till after you start the engine but might occur earlier if the battery is very drained. It is always in this state when your Prius is in ready mode)[/FONT]
11. [FONT=arial, helvetica] You can also test the battery by turning on the headlights, rear window heater and the heater fan. For a new battery the voltage would be around 11.3 (This is actually too low for a good battery that is fully charged). If the voltage drops below 10.2 it should definitely be replaced. For voltages in between the lower the voltage, the lower current charge of your battery. [/FONT]
12. [FONT=arial, helvetica] Push on the break pedal and push start. You should see Ready in the Speed display. The voltage should now read between 13.8 to 14.2 and higher in winter. This is the charging voltage! [/FONT]

JeffD

 

The inverter cooling pump is analogous to the water pump on the engine. The pump can be replaced without touching any of the inverter internals, and it is not hard.

The recall applies to 04-07 Prius.

It is possible to have inverter cooling problems on 2010, such as a hole in the radiator letting all of the coolant out. That happened to PriusChat user Flaninacupboard in the UK last month.

 

This is something I've only discovered. My 2005 has worked well in the past six years. Last week it wouldn't start. My wife took it in when after repeated tries over a period of half an hour, she got it going. The technician said the battery was just fine, and sent her on her way. The next day the car wouldn't start at all. A technician came to the house and opined it was the 12v battery. As an aside, rather than attempt to boost it so it could be driven the four kilometres to the dealer, he told my wife to call a tow truck. Back at the dealer, a day after the battery was "fine", the dealer claimed it needed to be replaced. And yes, this is also when we discovered how expensive the Prius 12v battery is.

I asked for explanations from the manager as to how the battery could be "fine" one day and "dead" the next, especially when the complaint to begin with, was that the car wouldn't start. We got no explanation. I then successfully argued - and I had to argue - that the dealer should be responsible for the towing charge, given it was incurred only because they simply failed to check the battery properly. While he wouldn't agree with my analysis, the manager had to admit it shouldn't have happened, and paid the towing charge.

A day later - my wife (who drives the car) noticed the keyless entry wasn't working. She took it to the dealer AGAIN. A technician looked at the car, tried the key and surmised that it could be "something serious" and told her to book an appointment two days hence. When she told me what happened later that day, it took me 30 seconds to diagnose the problem, with a flick of the keyless entry button on the dash. Somehow it had been depressed - possibly during the last service visit.

In any event, I don't expect my wife to read the manual. I was stunned that a technician at Toyota apparently hadn't. I was even more appalled at the indifference of the Manager who downplayed the inconvenience, or that it reflected poorly on the skill of the people working there. He offerred me a free oil change, an enormous prize. The dealer regularly hands them out to anybody with a Toyota and one of their frequent local coupons.