Swap Engine Ignition Imobilizer/EWS/keys from '01 X5 to '05 X5?

[ChezWhiz]

Bottom line up front:
I'm currently stranded at home with an otherwise drivable 2005 X5 that I can't start because the sole master key stopped working after I tried the Replacing Battery in Key fob DIY (see "2005 X5 Key fob Battery Replacement" below for more details about that). Now for the twist: I ALSO have an undrivable 2001 X5 (probable cracked engine block) that has 2 working master keys and a valet key.

Anyway, is it possible to swap the engine ignition immobilizers/EWS/parts(?) from the two vehicles and then take out the transponder/circuit board "insides" from one of the working keys and put it into the fob for the non-working key and end up with a working 2005 X5 until I can order a new set of keys from BMW? Will that work and does anyone have a link to a DIY article for replacing the appropriate parts?


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2005 X5 Key Fob Battery Replacement:
After I performed the DIY steps to replace the recharable battery in the key fob for the '05 X5, now I can't get the key to work at all (won't crank the engine, let alone accept programming via the and I can't be programmed using the Programming Key Remote DIY article). After I split open the key (before I swapped out the battery), I was able to hold the circuit board in place and use the key to start it - now nothing. I checked the battery voltage and it is fully charged at three volts. I've also checked all the fuses in the X5 (glovebox and rear hatch) and they are all working correctly. My assumption is that I either screwed up something on the circuit board while soldering in the new battery (I've since tried pulling it out and putting another one it so I don't think it's the solder job itself) or otherwise killed the transponder. Bottom line, I can't order a new key from BMW until Monday and it probably won't be until Tuesday afternoon or later before it can be delivered so I'm stranded at home for now.

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Colby,
[Dead] 2001 X5 4.4i w/ 139K miles (probable cracked engine block)
2005 X5 4.4i w/ 97K miles

[E46er]

Hi I know this is an old thread but you can't just swap out the immobilizers. They need to be realigned or synchronized with your DME via programming.

[Qsilver7]

The other issue the OP has in this scenario is...he's not considering that his two X5s have two different engines (DME/ECU). The 05 has the N62 double VANOS engine...whereas the 01 has the M62TU single VANOS engine. I doubt that the DME/ECUs will just swap over without some major issue.

It would have been simpler (and cheaper) just to buy a new key from BMW. If money is tight and the $100 + remote key is too much...there's always the other non remote key(s) that cost much less. The earlier models have the choice of an illuminated key, spare key with metal blade, or plastic spare/wallet key, or the limited use VALET key (only works the door & ignition). The later model years (10/2003-up) only have the remote keys and the plastic VALET key.

[TerminatorX5]

Electronic Vehicle Immobilisation System EWS 3.3

The EWS 3.3 serves as an antitheft alarm system and enables the start of BMW vehicles.
A transponder chip is integrated in each of the vehicle keys. A ring coil is fitted about the ignition lock. The transponder chip is powered by the EWS3 control unit via this coil, i.e. no battery is required in the key. The power supply and data transfer take place in the same way as a transformer between the loop antenna (coil) at the ignition lock and the transponder chip.
The key then sends data to the EWS3 control unit. If these data are correct, the EWS 3 control unit enables the starter by means of a relay located in the control unit and additionally sends a coded start enable signal via a data link to the DME/DDE. These procedures may result in a start delay of up to half a second.
Components

Data link to DME/DDE

The EWS3 control unit sends a coded enable signal to the DME/DDE via the data link. The engine cannot be started before this signal has been transferred.
Engine control unit (DME/DDE) with coded start enable input

The engine control unit (DME/DDE) only enables engine start if a correct enable signal is received from the EWS control unit.
EWS-DME/DDE interface

Identical variable codes are stored in the EWS 3.3 control unit and in the DME/DDE control unit. The value of these codes changes after every start procedure. Start enable only takes place if the code sent by the EWS control unit agrees with the code calculated in the DME/DDE control unit.
The control units are allocated only during initial programming of the DME/DDE control unit. The engine control unit then adopts the basic code of the EWS control unit.
Important
It is not possible to replace the DME/DDE or EW 3.3 control units for test purposes!
In rare cases, it is possible that the variable codes in both control units deviate from each other. In these cases, it is possible to reset both codes to the initial value via the service function DME(DDE) EWS III matching.
Key identification and start procedure

The following procedure takes place after inserting the vehicle key in the ignition lock:

• The transponder in the key is powered via the loop antenna and sends the key data to the EWS3 control unit.
• The EWS3 control unit checks the key data to ensure it is correct and only then sends an enable signal to the starter.
• The EWS3 control unit sends the variable code to DME/DDE. There, the variable code is checked against the saved variable code; if they match, the fuel injection is released.
• After the engine has started, the EWS3 control unit generates new key data (change code) and transfers them to the transponder in the key.
• A new variable code is also created and stored in the DME/DDE control unit.

Fault recognition in engine control unit

The following faults are monitored in the engine control unit:

• Interface, i.e. line to EWS control unit: In this case, the check is carried out in order to establish whether a signal is received and whether this signal is not subject to excessive interference.
• Variable code: A check is conducted as to whether the variable code which is sent by the EWS control unit agrees with the value calculated in the DME(DDE) control unit.

Engine start is inhibited if a fault is detected.