# Won't start after battery died and replaced.



## Firstbimer88 (Nov 2, 2016)

First off this is my first bmw and im sorry if this problem is a common sence fix or it was talked about before..i just didnt find it anywhere.so i bought a 2001 525i like 3 months ago and it was working fine.i did notice that the alarm thing on the key wasnt working but it didnt mayter cause i was using the key to lock and unlock the car..so i didnt use it for like 2 months and when i tried to started the lights would just flash but wouldn't start.it only started if i jumped started with another car..so a month later a bought a new battery and i opened the key alarm and it didnt have a battery and the inside of the key have some loose parts that needed soldering im guessing so i didnt mess with it.so now with the new battery everything turns on fine..except when i try to start the car..it doesn't even flash the lights anymore.it just turns and doesn't turn on..any help will be greatly appreciated and thanks in advance.

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## Orient330iNYC (Jul 30, 2002)

1) do you have the key with the remote buttons on the head?
2) did you cut open the head to try and replace the battery?

the key has a transponder chip in it. if it was damaged when opening the key, the DME will not let you start the car.


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## Firstbimer88 (Nov 2, 2016)

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## Firstbimer88 (Nov 2, 2016)

Orient330iNYC said:


> 1) do you have the key with the remote buttons on the head?
> 2) did you cut open the head to try and replace the battery?
> 
> the key has a transponder chip in it. if it was damaged when opening the key, the DME will not let you start the car.












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## Firstbimer88 (Nov 2, 2016)

Firstbimer88 said:


> Sent from my SM-G930P using Bimmerfest mobile app


When i opened it there was no battery in it. 


Firstbimer88 said:


> Sent from my SM-G930P using Bimmerfest mobile app


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## Orient330iNYC (Jul 30, 2002)

it sounds like you may have damaged the passive transponder chip in the key, this is seperate from the remote function, there's an antenna ring around the ignition that energizes the chip and does the antitheft handshake. if damaged, the key will turn, but the engine wont crank.


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## Firstbimer88 (Nov 2, 2016)

So it would damage it when i opened it even if they key worked fine before without a battery?

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## Orient330iNYC (Jul 30, 2002)

Firstbimer88 said:


> So it would damage it when i opened it even if they key worked fine before without a battery?
> 
> Sent from my SM-G930P using Bimmerfest mobile app


the battery is only involved in the remote functions. if the ews transponder in the key (which has nothing to do with the battery) was damaged when the key was opened, then no, the car will not start.

your key has three parts
1) metal blade thats cut to open the door locks and turn the ignition switch
2) remote control for remote lock/unlock. this is driven by a rechargeable battery
3) transponder for the coded drive away protection (ews)

#3 is passive, it gets its "power" from a ring by the ignition. when you turn the key, the car interrogates the transponder in the key. if it gets the wrong response or no response (damaged electronics) the dme will not crank the car
if you dont have any of the other keys (in 2001 they had two remote keys and a valet key, all with transponder chips in them) then you will likely need to get a dealer to order a new one

scroll to the bottom of this page to see the part that often gets damaged when people try to open the keyfob
https://www.bmwgm5.com/KF_WoS.htm


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## Firstbimer88 (Nov 2, 2016)

Orient330iNYC said:


> the battery is only involved in the remote functions. if the ews transponder in the key (which has nothing to do with the battery) was damaged when the key was opened, then no, the car will not start.


Oh ok..cool..yeah i had already looked up replacement key prices anywas and i think just replacing it is better than the people that say they can fix it..ill definately order the replacement key now..thanks allot..i appreciate the help..saved me a whole weekend or trouble shooting things and research..haha . thanks man.

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## Orient330iNYC (Jul 30, 2002)

be careful of where you order the key from. the car needs to be matched to the car and as far as i know the only place you can get it is from the dealership. you'll need proof of ownership (title or registration) and the vin number. if you order from them, i would also get the wallet key, its plastic, but opens the doors and will start the car. cheaper than two remote keys.
the keys on ebay and the like can be programmed to work as remotes, BUT need the chip swapped from a working key-- each car has 10 "key" slots in its dme, and unless the codes match, even if the key is cut correctly, and the remote is field programmed, the transponder wont be recognized by the car and it wont start


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## Firstbimer88 (Nov 2, 2016)

Oh ok...yeah this guy that people recomended on a vegas facebook group said he can replace it for 200 and the dealership was 320 with tax..

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## Firstbimer88 (Nov 2, 2016)

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## Firstbimer88 (Nov 2, 2016)

Orient330iNYC said:


> be careful of where you order the key from. the car needs to be matched to the car and as far as i know the only place you can get it is from the dealership. you'll need proof of ownership (title or registration) and the vin number. if you order from them, i would also get the wallet key, its plastic, but opens the doors and will start the car. cheaper than two remote keys.
> the keys on ebay and the like can be programmed to work as remotes, BUT need the chip swapped from a working key-- each car has 10 "key" slots in its dme, and unless the codes match, even if the key is cut correctly, and the remote is field programmed, the transponder wont be recognized by the car and it wont start


"Well program a chip to your car and see if it works for 75$ than you know if its the chip or immo Ring" ......he text me he can do this?..should i try this out or just get the dealership one?

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## need4speed (May 26, 2006)

Orient330iNYC said:


> it sounds like you may have damaged the *passive transponder chip in the key,* this is seperate from the remote function, there's an antenna ring around the ignition that energizes the chip and does the antitheft handshake. if damaged, the key will turn, but the engine wont crank.


This is my first thought as well. Actually I didn't know what it is called, but that function.


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## Firstbimer88 (Nov 2, 2016)

need4speed said:


> This is my first thought as well. Actually I didn't know what it is called, but that function.


I might just got to the dealership though..saves me from any more hassle

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## Orient330iNYC (Jul 30, 2002)

shop around the various dealerships, prices can vary


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## Firstbimer88 (Nov 2, 2016)

Cool..I'll definitely do that..thanks again

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