replacing battery in key fob....

Hi there,

Im new to this forum and find it can be very helpful with issues, so....

Ive just bought a BMW 330ci Auto (2002) and only have one key. Ive managed to purchase some blank keys and also another key fob with the transmitter from eBay.

The blank keys have been cut and open the doors etc correctly. I then reprogrammed the second key using the method posted by MAXXED

This has programmed the after market key and the lock/unlock work, however the key doesnt start my car....

Any ideas ? SHONKY mentioned programming the EWS ? is this easy to follow and apply ? or is there more I need to do to get the car started with the after market key ?

Thanks in advance
Manish

Great thread. Just used this on a key from 2000 and it worked perfectly. I bought the CR2025 battery instead of the rechargeable VL2020 battery so I'll have to eventually open it up again. Programmed it using the 2 key method in the original post.

MINIzguy: Not a great idea. The circuitry is still there to charge the battery and so your non-rechargeable battery will be getting charged every time you drive. At best it will probably leak eventually.

mraghvani: If the keys are truly blank, you can program the key using a special device (an EWS programmer can read/write keys and the EWS). However to program a key, you need to pull the EWS out of the car to get the codes to program into the key. EWS programmer is about $150-200 and is not a BMW tool.

Hey Shonky,

The second key, when bought off eBay might have been programmed before as I was also given a 6 digit code (I have no idea what its for). I then removed the circuit board and placed it into a blank, which was then cut and programmed with the 2 button method. All works, just not starting the engine

Is the EWS stuff pretty easy to go thru ?

Do you know of any links on a 'How to' for blank keys ?

To go thru the EWS bits, is the BMW Scanner 1.4.0 go enough to use ?

Thanks in advance
mraghvani

To recode or read the EWS (to program keys) you have to remove it from the vehicle. You need a special EWS tool to read/program keys and to read/program the EWS.

6 digit code? I don't know what that would be for. The keys (as in the numbers/codes inside the key and EWS) are much longer than that. The circuit board is mostly the remote control section. The actual RF ID bit is usually separate in a corner near where the metal part of the key comes out of the plastic so it's close to the antenna inside the ignition switch. It's a self contained part and looks like a small integrated circuit chip with a corner cut off but with no pins. That's what the car talks to. Like this

Also, reprogramming the EWS was never intended to be possible by BMW. Hackers have just figured out how to do it.

BMW's plan was 10 pre-programmed keys in the EWS. If you needed a new key, they had a database of the pre-programmed codes and could just manufacture a new key and send it to you based on the VIN without touching the car.

Thanks for the info and appreciate the answers.

So basically I have no choice but to go to BMW and get a 2nd key ordered which will start the car. Ah well as least I'll have a spare which unlocks / locks the car but doesnt start it

Damn and I even bought the OBD cable and software, thinking I could give it a try.

After reading the whole thread, people are saying to get the Horizontal battery or the Vertical battery.

Does anyone know which one is the correct one to buy?

Regarding the battery, I purchased a couple of these from eBay :

http://www.ebay.co.uk/itm/2607609691...84.m1439.l2649

and although its made a brillant improvement to unlocking/locking, I did have to make some modifications to the terminal connections on the battery so it would fit the circuit board. If your ok with a soldering iron, then you shouldnt have any worries.

Horizontal or Vertical?

I dont know and dont know the difference, but the one I ordered from eBay just works

Originally Posted by djarndtsfo

--------------------------------------------------------------------------------

i too needed to replace one fob's battery and found this thread and it was very helpful. I was able to open up the key fob and unsolder the battery and was about to order the horizontal battery from mouser or digikey. Before i did, i researched the battery on the panasonic battery site and found that another non-rechargeable is essentially the same size and voltage. I picked one up at my local drug store (2025 or equivalent). Now, here is the part that you may or may not want to try (see picture). After removing the battery, i used needle nose pliers to roll the welded tabs off like you do to open a can of sardines (those who remember using the included key to remove the metal strip around the can). I then smoothed them back out flat and soldered both battery contacts back on without the battery (you may actually trim off the battery contact wrinkly part if you want). This makes like a slip-in battery holder. I slipped in the battery, wrapped a rubber band around the fob and tried it. It works great! Yes, i know this is not a rechargeable, but i could not find anything on the circuit board that takes an outside electrical source that could possibly recharge the battery (i will do some more research, but i don't think it has to be a rechargeable type battery). The only other significant difference between the rechargeable and the 2025 lithium i used is a specification for nominal capacity (mah). The rechargeable is lower at 7 as opposed to the 2025 which is 165 mah which means it should last longer! Well i have been using mine for a total cost of less than $3 now for over 7 months and it's still going strong. Just in case though, i used a silicone sealer type adhesive that is strong but removable if i have to change the battery. The beauty is that if there is a next time, i just slip out the old battery and slip in a new $3 battery and reseal (no more soldering). The plastic holder the fob has for the battery space puts enough pressure on the slip-in cell so you don't have to use the solder variety. Hope this helps - good luck. Donald (electronics engineer) san francisco.

+1

If you have some of theses problems, ive made a list of ideas and hits to make this DIY easier!
*EVERYONE SHOULD CHECK TO MAKE SURE THE SOLERING POINTS DIDNT BREAK ON THE BACK OF THE MICROCHIP BOARD. MINE WAS, AND I COULD HAVE AVOIDED CHANGIN A PERFECTLY GOOD BATTERY!!! All I needed was a small re-solder of the Negative tab where it connects to the board.


1."Fob is hard to open or I keep cutting my fingers"
-Try to use an actual Carpenters Knife with a NEW razor, and only let the blade out ONE click. This makes the blade easier to handle and theres less risk of going so deep you cut the microchips/ so ive seen. And take your time..

2."Im having trouble with getting the old battery out"
-Use the razor flat against the battery and slice the spot welds. Take your time.

3."Key still doesnt work, tried reprogramming and it didnt work."
-Make sure the battery is making good contact and is not reversed. My battery is positive side up/..

4."How sould I re-seal the key"
-CrazyGlue/ or Gorrila Glue. Run a small bead around the bottom part of the FOB, then lay the top part with the buttons down to the glue. Use a zip tie around the butt of the key if yours isnt broken. Then clamp the front, Not on the buttons. Use this because othe things will ooze inside the key as they dont dry fast.

Futhermore.. I did not remove the OLD tabs, Nor did I solder ANY tabs to the new battery. I used a generic 2025 and just slid it between the old tabs. The pressure of the outer case keeps it tight enough to ensure good contact.

EASY is, as EASY does

Using a normal battery instead of a rechargeable is possibly not all that wise. An electronics engineer would know that.

The circuitry is definitely there to charge the battery and eventhough you have put a non-rechargeable battery in, it will still charge it which is probably the reason it is still operating. A normal battery will take an amount of recharging to a point where it will probably leak.

Also The 165mAh rating comparison is invalid. This is based on one charge. You are comparing the non-rechargeable running from 100% to 0% once (how it should be operated). The rechargeable battery can do this many hundreds of times.

All that said, my old E36 remote batteries where never replaced in the 6 years I had it using one key only. The E36 definitely did not charge the remote battery in the key. Not really sure why they changed to rechargeable actually.

eh.. not too worried about the battery melting like a junior mint. all i know is ive made it around the $280 stealership whammy. i think the battery will work just fine. The charge will fade away over time and need to be changed a lot sooner, im guessing, but im happy if i get a month outta it. remember to be poor you sacrifice proper operation for function... yes i know the rechargable is $2 more.. every penny counts !!

Genuine batteries seem to last in the 5-10 year range. Replacing the battery with the right one should give you that much again. Even if your non rechargeable is lasting a year before finally dying, you're a long way behind after saving your initial $2. If you get a month making you happy, you'll be a long long way behind.

Also it won't "melt". Depending on the battery chemistry it may leak something corrosive potentially damaging the electronics.

Your money, your car and your key though, so good luck.

I was planning on doing this DIY, because I tried all the ignition tricks and it didn't work.

But when I disconnected my battery to change my fuel pump the key remote started working again

Disconnecting battery was prob recommended, just wanted to throw in my success story.

I love this thread

I had a spare key that the previous owner said was broken. I was going to cut it open and replace the battery, but wanted to try synchronizing it first. I followed the steps outlined, but still wasn't getting a response.

I then tried the synchronization process using the working key first, and viola. I now have two working keys.

The best part being that the previously non-working key doesn't have the annoying child lock programmed into it.

Thanks

Originally Posted by VIKTR

The best part being that the previously non-working key doesn't have the annoying child lock programmed into it.

Please explain. What kind of 'child lock' would a key have on it?

Originally Posted by ShaTR

Please explain. What kind of 'child lock' would a key have on it?

With my other key, the car would automatically lock all the doors when I drove off.

With the key I now use, the doors don't lock unless I lock them.

I had thought that the function was programmed into the car, but I do remember reading in the manual that the car can be programmed to where different keys have different settings.