Help diagnosing HV battery issue on 2006 Prius

yes, anyone can buy a 12v from toyota parts department.

 

Auto zone has a good agm battery that I was able to get for $140 after core, New Years deal and $20 in store credit.

Worth a call.

 

Here you go:

https://m.autozone.com/batteries-starting-and-charging/battery/duralast-platinum-battery/766475_188278_0?location=

With pictures :



Good luck .

 

Two points. One just specific to this thread:

The evidence even for that isn't as strong in this thread as you're making it sound. It started with an ACCessory-load reading of 11.8, which is about what I would see on my 2010 if I walked out and measured right now, which got pronounced "dead as a doornail" or "essentially flat" by some voices in the PriusChat gallery, while another voice seeing the same evidence said "I would hold off on replacing the 12 volt battery", and that's where I'd come down on this evidence too.

Significantly, the OP didn't even specify how he took that 11.8 reading (battery terminals? MFD screen? it makes a several-tenths-of-volt difference), and none of the commenters here asked for that information, before offering judgments that hinge on smaller differences than that.

The traction battery "needs" to be replaced because its ECU has flat-out said so, and produced the freeze-frame voltage readings to show it, and exactly which module is bad. The "need" for the 12 volt to be replaced right away is a much more open question.

But the bigger point concerned this:

Yes, the endlessly recycled business about "false codes". We're in agreement that it's claimed here quite often. If being claimed often made stuff true, it would be the truest factoid in all of PriusChatdom. It would even be extra more true just because of this very thread, where it's been repeated five more times:

• #9 "When the 12 V battery starts going bad strange things happen."
• #12 "there is no exact science, but at some point, the computers start going haywire when they don't receive proper voltage."
• #25 "Most likely some of the others, but likely not the P0A80."
• #46 "(that often sends all kinds of incorrect info)"
• #52 "The false codes have been reported here quite often."

But, in any of those five mentions in this thread, is there any evidence offered that this claim is, you know, true? Beyond just repeating it more times as if it were established?

Well, what does it matter, you may say, when it's been reported in so many other posts before?

Ok, how many of those posts have you seen that offered any substantiation, besides just repeating it because of other posts that repeat it? Any? Even one?

I've been watching for several years, and occasionally pointedly asking, and haven't seen one yet. If you know of some I've missed, I'd love to see the links.

What would substantiation look like? It's dead simple. If the claim is that an ECU under some low battery voltage "often sends all kinds of incorrect info", it ought to be pretty easy to give an example, no?

How do you show that a report from an ECU was "incorrect info"? Well:

• You start by retrieving the info. You can't show it's incorrect otherwise. (This weeds out posts where somebody "decided" their ECU "must be" sending incorrect info, as an alternative to bothering to retrieve it.)
• Then you find out what the repair manual says are the triggering conditions for the codes you got. (This weeds out posts where somebody read some codes, and then "decided" they made no sense, rather than taking the first steps to make sense of them.)
• Last, you report on the actual testing you did to show that those triggering conditions did not exist in the car in question, and therefore, the reported info was incorrect. Those three steps, and the claim is supported.

I would read some posts like that with great interest. Meanwhile, though, this is a claim that just keeps being warmed over and flung in the path of new PriusChatters who could otherwise be getting help finding out what's wrong with their cars, and I think it's a shame.

-Chap

 

The frequency of data reported here certainly matters. The OP's12v is dead and being replaced along with the HV. Are you suggesting he should also blindly replace all the other parts/systems indicated, too? If you want more proof of false codes, use the search function.
"Master Warning, Check Engine Warning, and Brake System Warning lights... the codes:
-B1421, B1650, C1241, C1242, C1300, U0100, P0A80, B1442, P3000, U0111, B1660

 

The OP's 12 v battery is in debatable condition, and the OP has been talked into replacing it, which is fine.

Have you seen me suggest anybody blindly replace anything, ever? See above: after reading trouble codes, what is the next step? You don't get much help from the fortune-cookie one-line descriptions given for most codes; you go look up what conditions actually trigger the code.

If you get, for example, a DTC whose fortune cookie is "oxygen sensor" (just as an example), that doesn't mean you go buy an oxygen sensor and screw it in. It means you read about what engine conditions monitored by the ECU lead to that code being set, you consider all the stories that could lead to those conditions existing, do your gumshoe work to rule out the ones that don't fit, and fix the one that's left, whether it's wiring, sensor, intake leak, whatever it turns out to be.

When you have a car with a bunch of codes (the exact point where the "false codes" enthusiasts would throw up their hands), pause to be thankful for what is usually a beautiful diagnostic gift: once you take the actual time to read up on the triggering conditions for all of those "false" codes, the number of stories that fit the whole set will be far smaller than the number you usually have to rule out with a smaller set of codes.

Do you have a search result in mind, by chance, that meets the three prongs of "proof of false codes"?

• Codes were retrieved
• Actual trigger conditions for codes were looked up and understood
• Trigger conditions were shown not to exist in car, therefore "false codes"

If you know of one, you could save me time with a link, 'cause I've tried before.

-Chap

 

That is a problem when you have all these armchair detectives whose sole source of information is what they read on the internet. It is the fodder of urban legends, such as a bad 12 V battery is the source of all that ails a Prius.

I would like to make another point, all these "helpful" suggestions to "check the health of the 12 V" et al quite often cause so much clutter in the thread, to the point, pertinent questions get missed and go unanswered while pages and pages of "helpful" people ask all sorts of irrelevant 12 V battery questions of the OP.

It is particularly annoying when there is no particular information that points to the 12 V battery.

I'd just ask, that if the only experience you have is that you read it on the internet, please hold back your urge to contribute, if all you got is some inane 12 V battery contribution. You are of no real help to the OP if you derail their thread.

 

Sounds like we need a separate thread to debate false codes caused by low 12v battery.

 

I wonder what a good forum for that would be ... affects all generations of Prius, or at least of Prius owners ....

-Chap

 

Starting with MY 2004, the general troubleshooting procedure in Toyota’s Repair Manual (under “How to Troubleshoot ECU Controlled Systems” in the Introduction) includes a step to “Inspect Battery Voltage,” right after “Vehicle Brought to Workshop” and “Customer Problem Analysis.” They write, “Standard voltage: 11 to 14 V. If the voltage is below 11 V, recharge or replace the battery before proceeding.” The manual doesn’t give a reason for this step, but it may be the origin of the oft-repeated—and at times, tedious—suggestion.

 

Notice it does not say, "your battery is shot, replace immediately." The "recharge or replace the battery" implies further diagnosis steps to determine which of these options is appropriate.

 

Wow! I started a lively discussion.

Both myself and Eric did comment that the diagnosis of a failed HV battery could be easily rechecked with a simple code reader. Not a bad idea before spending $2500.

With all the discussion of a weak 12 volt battery causing false codes no one took the time to really look at the OP's codes.

Let's look at them one at a time.

B1421 The AC solar sensor is in the shade.

B1442 AC Damper Servomotor Circuit. This seems unrelated to everything else.

B1650 The passenger seat Occupancy Detection system has an error.
B1660 Passenger Airbag ON / OFF Indicator Circuit Malfunction

Has the car been in an accident? Is the pregnant lady wearing a seat belt warning light on? Was the light on before the current problems with the car? It could be the passenger seat weight sensor needs to be calibrated.

C1241 LOW BATTERY POSITIVE VOLTAGE OR ABNORMALLY HIGH BATTERY POSITIVE VOLTAGE
It would help to know the sub code also. A lengthy test procedure can be found here.
https://murdercube.com/files/How-To/Automotive/Toyota.Corolla.2004.Complete.Repair.Manual.Collection/Repair%20Manual/05%20-%20Diagnostics/ABS/C1241%20Low%20and%20High%20Voltage.pdf

C1242 IG2 Power Source Circuit. Both the C1241 and C1242 codes deal with the ABS system. A drop in the 12 volt system voltage IS a possible cause.

C1300 Malfunction In ECU. Output by the Skid Control (ABS) ECU when it finds an internal malfunction.

U0100 and U0111 Can bus communication errors between the Engine Control Module and the Battery Control Module. U codes can be very difficult to track down.

P3000 sub code 123. This is a just a me too code caused by the P0A80.

P0A80 Replace Hybrid Battery. The dealers printout showed block 12 dropping out. The problem can be confirmed by looking at live battery data while doing a forced charge and discharge. The readers are cheap and the test takes just minutes.

The B codes are not related to the cars current problems and unlikely caused by a 12 volt problem.

The P0A80 is not caused by a weak 12 volt battery. It's also very easy and cheap to double check.

The C and U codes could be caused by a weak 12 volt battery. (It's one possibility listed in the repair manual) They could also be riding along with the P0A80 code. It's not unusual for a bunch of codes to be caused by one root problem. I have seen a similar but not the exact set of codes caused by a faulty Skid Control Computer.

It could take quite an effort to determine the cause of everything going on with this car. The 12 volt and HV batteries should be replaced one at a time with several driving cycles completed between the replacements. Check for returned codes before replacing the second battery.

I suspect the B codes will remain after both batteries are replaced.

Brad

 

congrats! you put in a new 12v?

 

oh boy.

 

Thank you for posting the update!

Glad to hear everything went smoothly, and that your MPG is back in the 50's.

Pretty sure you won't be having any HV battery issues in the near term.

Looking over the HH website it appears a gen2 rebuilt is going for about 1k with free shipping both ways (core returned) and comes with a 1 year 25,000 mile warranty.

Then I read the FAQ and couldn't find any additional warranty info beyond the initial sale, like making a warranty claim and who pays for shipping (both ways again) and the labor costs to remove and replace the warrantied battery - and then the recrating of such for return shipment.