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AMD
AMD, Toyota Certified
Category: Toyota
Satisfied Customers: 2724
Experience:  Master Automobile Technician L1 Advanced Level Specialist
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Toyota prius 2012: I have a prius 2012 model and there are

Customer Question

I have a prius 2012 model and there are some problems with P-Lock
I have been parking my car for around 2-3 months while going overseas for work

(1) P-Lock malfunction (the car can drive but the P-Lock alert keeps coming on)
(2) The brake is stiffer when pressed the brake pedal. you have to push a little bit harder for the car to come to a stop

I have found some answers about problem with 12V battery, but are there any other issues that may cause the problem?

Also i would like to know what does the 12V battery job is and what function of the car is it controling?
Submitted: 11 months ago.
Category: Toyota
Expert:  AMD replied 11 months ago.

AMD :

Hello and thank you for trusting us with your Toyota question, My name is XXXXX XXXXX I will be assisting you today.

AMD :

Are you available to discuss your question at this time?

Customer:

yes thank you very much

AMD :

Hello! How are you doing today?

Customer:

Hi AMD it's been a good day so far

AMD :

Wonderful! If I may ask, how many miles or kilometers on your vehicle?

Customer:

just around about 26000 km on the Prius 2012 that i'm driving now

AMD :

OK I See. Just to verify, you mentioned that you leave your vehicle parked for 2-3 months without being started or anything?

Customer:

just bought them at the end of last year

Customer:

yep that's right

Customer:

without being start - -"

AMD :

OK. I am a hybrid certified technician and I specialize in Prius vehicles like yours. I will explain what I think is going on here then I will go on to explain what does the 12V battery does.

Customer:

Very relieved to get some info from an expert thank you very much sir

AMD :

First I agree that the 12v battery is the issue. The vehicle was not designed to be left for 2-3 months without being run, And the 12v battery in your prius is a known weak point. It's a very small battery that doesn't last a very long time and I will explain why it's so small. Typically in a situation like yours where you would leave the vehicle for a very long time, you either disconnect the battery or utilize a battery maintainer. A battery maintainer is basically a small device that plugs into the wall and then onto the battery that will keep a very small charge on the battery to keep it from dropping over time

AMD :

the reason it drops over time is because even though everything is off in the vehicle at least one out of the 33 computers on board is awake and ready to detect the key and start the vehicle.

AMD :

So it will drain a very small amount and over 2-3 months it will be enough to bring the battery voltage down enough to cause all kinds of abnormal issues

AMD :

Making sense so far?

Customer:

making very good sense so far sir

AMD :

OK now let me talk about what that battery does.

AMD :

The 12v battery has a very basic function in life in your car. when the hybrid system is OFF meaning the READY light is OFF it will power the interior electronics like the radio and lights. When you start the vehicle the 12v battery will power up the computers to start the hybrid system, the 12v battery function STOPS as soon as the READY light comes on and then the hybrid system will charge the small 12v battery from the high voltage battery. Does this make sense?

Customer:

right, so when the car is started and ready to run, the 12V batter does not have any function to do with the car at all

AMD :

That is correct. However let me point one thing out and this is something that comes from experience.

Customer:

yep

AMD :

When you turn your prius on, the on board computer does a comprehensive check of all components and then if it sees any issues it will illuminate a warning light. When the 12v battery is low, common for the computer to act abnormally because of the low voltage.

AMD :

So for example it could cause the car not to ready on. it also could cause the p malfunction.

AMD :

Do you have any questions about the 12v battery before we talk about the brakes?

Customer:

nope, because the reason i'm asking about the 12V battery is that, i'm wondering if it has anything to do with the stiff brake pedal

AMD :

If I may ask, are there any warning lights in the dash once the vehicle is running and driving?

Customer:

nope there are no warning lights once running and driving

Customer:

but

Customer:

when the car almost coming to a stop when pressed the break pedal

Customer:

the p-malfunction alert comes on

Customer:

with a beep sound, then disappear

AMD :

OK I See. I see that you've listed your country as Thailand, Is your Prius purchased new in Thailand or is it an import from another country?

Customer:

purchased new in thailand sir

AMD :

OK, I am in the US so I wouldn't know how things are in your country so excuse me for asking, Was the vehicle purchased at a Toyota dealership?

Customer:

yep it was purchased from the official toyota dealer

AMD :

OK again things might be a bit different from my country and your country but the company is the same so the vehicle should still have it's manufacturer warranty in effect, Did you take the vehicle back to toyota's service center for an inspection?

Customer:

yep i do check the car regularly with the dealer and warranty is still in effect

AMD :

OK Regarding the p lock malfunction the dealership will need to run a health check to see if there are any codes present and follow up with diagnosis from there. It could still be a weak battery throwing the on board computer off but without an in-person inspection and an interaction with the on board computer of your vehicle it's really hard to tell exactly what is going on.

AMD :

So what I suggest you do is this

AMD :

First stop by your local dealership, have them test the 12v battery or it's called Auxiliary battery in Toyota terms.

AMD :

If the battery fails the load test, have them replace it as it should still be under warranty.

AMD :

Then have the dealer run a health check on the vehicle using their equipment and go from there.

AMD :

if they come back to you and tell you everything checks out fine, then take a drive with one of their technicians and show them the issue with the p lock malfunction.

AMD :

sometimes they need to be checking for issues while the p malfunction happens because other times when it disappears there will be no error codes in the computer.

AMD :

Also consult the dealership for a suitable battery maintainer. basically explain to them that you could leave the vehicle for 2-3 months at a time and have them recommend a suitable maintainer for your vehicle to use and show you how to use it correctly so you can maintain the battery should you ever travel again so the battery wouldn't give you issues.

AMD :

Did you have any other questions for me today?

Customer:

just one more thing about the break

Customer:

what might cause the stiff brake

AMD :

OK Let's go into that with a bit more detail, When you say stiff, do you mean the pedal is hard to press? or do you mean the vehicle is hard to stop and you have to press it harder to make it stop?

Customer:

and also when i try to break lightly, you know the hydraulic ish squish sound when you push the break on prius

Customer:

sometimes it do the break by it self keeps squishing on and off rapidly

Customer:

and the p-malfunction comes on

Customer:

the vehicle is hard to stop and you have to press it harder to make it stop?

Customer:

sorry, yes i mean the vehicle is hard to stop and you have to press it harder to make it stop

AMD :

OK How many kms have you travelled since you came back from leaving the vehicle 2-3 months?

Customer:

should be around 5000 kms

Customer:

yep should be around 5000kms or a bit less

AMD :

OK I think we might have a problem with the electronic controlled brakes. Typically any issue with the brakes will set multiple warning lights but just like the p malfunction issue, we will need a more in depth inspection of the issue. I can tell you this

AMD :

From my experience with your vehicle there are no known issues that match the issues that you have. Whatever the vehicle will need it should be covered under warranty at the kms you have and the year so you shouldn't worry about costs.

AMD :

However it's very important that you explain to the dealership exactly what you are experiencing and it would be best to take a technician for a drive and show them.

AMD :

I doubt the brake problem is related to the 12v battery, but again without an in person inspection it's really hard for me to tell exactly what's going on

Customer:

yep i'm quite clear now what to tell the technicians

AMD :

Did you have any other questions for me today?

Customer:

that's about it thank you very much sir

AMD :

You're welcome. A positive rating for my input would be greatly appreciated.

AMD :

Thank you for choosing justanswer.com

Customer:

sure AMD

AMD, Toyota Certified
Category: Toyota
Satisfied Customers: 2724
Experience: Master Automobile Technician L1 Advanced Level Specialist
AMD and 5 other Toyota Specialists are ready to help you

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