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Old 11-18-2013, 08:39 AM   #1
bostonsthename
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Programmed Keyfob but Key won't start car!!! HELP!

So when I purchased my current car, neither keyfob worked (I have 2). With one of them the PO tried to replace the battery but not successfully. So I just took my keyfob from my old car with a good battery and cut it open. I removed the whole circuit board and paired it with my spare key and programmed it to my current car. Worked great. I can lock and unlock doors with it.

Here's my issue now. My key with the non working keyfob will start my engine no problem, but if I try the key (my spare with the working keyfob) first, then it won't turn over. However if I use the key with the bad battery it'll start right up, then if I shut it off and switch keys, it'll start right up again, but after I shut it off, lock the doors, then come back to it, it won't start with that key.

Any ideas?!
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Old 11-18-2013, 08:48 AM   #2
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The EWS chip in the key is no good or you damaged it when you took it apart. You need a new key or send it to Scott at GM5 repairs and see if he can fix it.
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Old 11-18-2013, 08:51 AM   #3
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The car will start with that key, but it's like it needs to be started with the other key first. With a bad EWS chip it will still be able to start the car?
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Old 11-18-2013, 10:35 AM   #4
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Does using the whole circuit board from the old key have something to do with this not working? I was able to start the car with that key prior to the programming with no issues.
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Old 11-18-2013, 01:49 PM   #5
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There are two circuits on the board in the key. One is a passive RFID circuit which the EWS systems checks and allows the car to start. The other is battery powered and is responsible for the remote functions. They do share a coil used for EWS communication and battery charging. See Scottjoh posts and site http://www.bmwgm5.com/Key_Repair.htm.
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Old 11-18-2013, 02:16 PM   #6
bostonsthename
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key #1: good battery, circuit board from keyfob of different car.
key #2: bad battery, circuit board original

Key #2 always starts car, Key #1 only starts car if key #2 started car, car turned off then key #1 used to start car. Key #1 won't start car if it is the first one used.
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Old 11-18-2013, 02:36 PM   #7
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Programmed Keyfob but Key won't start car!!! HELP!

Quote:
Originally Posted by bostonsthename View Post
key #1: good battery, circuit board from keyfob of different car.
key #2: bad battery, circuit board original

Key #2 always starts car, Key #1 only starts car if key #2 started car, car turned off then key #1 used to start car. Key #1 won't start car if it is the first one used.
Programming the key is only for the remote keyless entry. It does not have anything to do with starting the engine!
After the EWS authenticates a key it unlocks the starter and DME for about 30 seconds. After the starter and DME are unlocked you can use anything that can turn the ignition will start the engine.

Last edited by scottjoh; 11-18-2013 at 02:36 PM.
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Old 11-18-2013, 02:36 PM   #8
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Key from another car will not start your car. The transponder chip on the board is pre-programmed from dealer and can't be feasibly altered. You can only synch (program) the remote functions with your car.
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Old 11-18-2013, 02:43 PM   #9
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Key from another car will not start your car. The transponder chip on the board is pre-programmed from dealer and can't be feasibly altered. You can only synch (program) the remote functions with your car.
The key itself and the keyfob shell are from my current car. The circuit board inside is from my old car. So when the key is entered into the ignition, the car reads the signal from the transponder chip (which is soldered to the circuit board) inside that keyfob and determines if it will start or not, even if it is the correct key? Plastic valet keys don't even have a chip in them but they'll still start the car.
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Old 11-18-2013, 02:48 PM   #10
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yes,and all keys have the chip.
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Old 11-18-2013, 04:40 PM   #11
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Originally Posted by bostonsthename View Post
Plastic valet keys don't even have a chip in them but they'll still start the car.
NOT CORRECT! The plastic spare key and the valet both have transponders in them. If the key did not have a properly programmed transponder chip it would not be able to unlock the starter and DME.
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Old 11-18-2013, 05:13 PM   #12
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^this.
The irony of someone who has no clue what's happening, claiming false facts about the valet key...
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Old 11-18-2013, 05:13 PM   #13
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Yes the plastic wallet/spare key does have a transponder chip in the head of the key. If you look closely you can see the spot where there is a plastic plug covering the transponder location. The plastic key transponder is more like the the stand along transponder capsule. Note that not all E46's can order a plastic wallet/spare key. BMW dropped this key sometime is late 2003 as I recall.
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Old 11-18-2013, 06:05 PM   #14
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^this.
The irony of someone who has no clue what's happening, claiming false facts about the valet key...
Ok, you were talking about the other guy, not me.
I only speak about things I know to be fact. You will get no BS from me
All keys have transponders in them. The one in the valet key is well hidden and molded into the rubber head. On the plastic key it's a lot easier to see. See picture below of the spare key.

Last edited by scottjoh; 11-18-2013 at 06:51 PM.
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Old 11-18-2013, 06:07 PM   #15
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Who's this A$$ that speaks about things he knows nothing about. I only speak about things I know to be fact, no BS.
Not you Scotty! I was looking in OP's direction.
Sorry bout the confusion there mate
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Old 11-18-2013, 06:20 PM   #16
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Scott is the key man!!
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Old 11-18-2013, 06:23 PM   #17
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Same here OP. I had 1 of the two original keys opened and replaced the rechargeable battery so now its nice having the keyless unlock/lock features again but sometimes it wont start the car on any given day. The 2nd key which doesn't work for keyless entry anymore ALWAYS starts the car, so I personally went thru diagnosing and praying it wasn't the starter after trying the 2nd key I lucked out. So now I have both in the same key ring and feel like a d**** till' I can afford to replace it with a brand new key. So I use the first one to open the car, and 2nd to start. Like back in the old days when cars came with a door key and ignition key, retarded I know.

Only solution I know of is to buy a brand new uncut key and have it cut and programmed to your car.
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Old 11-18-2013, 06:59 PM   #18
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Quote:
Originally Posted by Manny04 View Post
Only solution I know of is to buy a brand new uncut key and have it cut and programmed to your car.
Why don't you do what most normal people do and just purchase a new keyfob from the dealership? Order it before noon Mon-Thur, likely will be there by the following afternoon. Key is already cut, will start the car, only need to program the keyfob to activate the locks, not tools required, about 30 seconds of work.

People make this key thing WAY harder than it needs to be and you really do not save much trying to do the key yourself. Just depends on what your local dealer is trying to stick you for a key. But read below and there are options.

http://forum.e46fanatics.com/showthr...ghlight=keyfob
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Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

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Old 11-18-2013, 07:07 PM   #19
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Ok, sorry I was misinformed about the valet key, I didn't realize it had a chip in it. In the standard diamond keys the chip is attached to the circuit board, which is in no way connected to the physical key. So why is it that this key that once did work with no issues starting the car won't start it now. Does the car read that the chip from the other car is attached to the physical key? I might just order a battery and solder it to the circuit board that it originally had and see if I can program it, because I know that one came with my current car. I'm not looking to shell out 200 for a new key. I just wanted a remote in case my lock cylinder in the door decided to break.
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Old 11-18-2013, 07:12 PM   #20
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Quote:
Originally Posted by jfoj View Post
Why don't you do what most normal people do and just purchase a new keyfob from the dealership? Order it before noon Mon-Thur, likely will be there by the following afternoon. Key is already cut, will start the car, only need to program the keyfob to activate the locks, not tools required, about 30 seconds of work.

People make this key thing WAY harder than it needs to be and you really do not save much trying to do the key yourself. Just depends on what your local dealer is trying to stick you for a key. But read below and there are options.

http://forum.e46fanatics.com/showthr...ghlight=keyfob
Money is the issue here. New key would cost nearly $300. A guy on eBay replaces the rechargeable battery in the remote for $50. Was not expecting him to damage the ignition function in the process though
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