Weird Key troubles. Advice needed.
 

So I have my key that works just fine. Fob works and key starts the car. My wife's key fob works and will lock and unlock just fine. But you take that same key and try to start the car and it does nothing. Nothing at all. The key turns but the starter does nothing. You put my key in and it starts just fine. Another piece of information that may or may not be relevant- the drivers seat adjuster stopped working a month and half ago which includes the steering wheel adjustment too. The wife's key just stopped working a few days ago.

So what do you think the problem is? What will it take to get the key working again? What are your thoughts?

Thanks!

These are two unrelated issues you're having. The key might work for locking/unlocking the car but no for starting it, which means the internal transponder failed, you'll need a new key.

For the driver memory and steering adjustment what failed is the seat memory module than controls both things, you need to replace it as well, is plug and play, so no worries about programming or anything, just keep in mind that if you look for spares in a junk yard that you take the latest part number available for these cars, since all the other older versions like you probably have, tend to have the same issue that is a weird limited eeprom space for the adjustments of seat, steering wheel and mirrors.

Part number might be this one: 61317119867 (I changed mine too)

If the immobilizer circuit isn't working in the key it's likely a bad solder joint. It can be disassembled and reflowed. Usually it's the other ckt that breaks (fob remote)


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Just put the working key by the antenna ring and see if the bad key can start the engine. If the engine starts that mean you have an EWS issue with the old key.

There is no immobilizer circuit board in the key. The only immobilizer is the chip which is not attached to any circuit. See image of the chip.

http://www.autokeymall.com/Upload/Pr.../31/7939VA.jpg

Explains how it still works when the electric circuit isn't working. I thought that got power from the induction circuit


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The OP states they have a 2005 X5...which means if they have original BMW remotes...then their remotes are the new style (diamond shaped) remote keys.

The new style keys don't have a loose EWS transponder like what you pictured. The BMW keys that have a loose transponder chip (during the e38/e39/e46/e52/e53 generation of BMWs) are only found in the old style remote keys and all of the non-remote keys. :)


The new style (diamond shaped) remote key's EWS transponder is soldered to the remote's internal IC board...just like the key's internal battery is also soldered to the IC board (see pics below):


http://www.bimmerboard.com/members/q...%20Diagram.jpg

The chip get it power from the antenna ring. The induction circuit is used to charge the battery for the key fob. You can have a dead key fob battery, but the chip to start the engine will still send out a signal to the EWS module because it is receiving the electrical charge from the antenna ring.

You can see from this photo that the chip is a stand-alone chip that is not solder to any circuit board.

http://www.bimmerfest.com/forums/att...1&d=1297208685

The pic you have posted is NOT an original BMW new style remote key...that is an ebay key (replica) that has a space designed in it to place a transponder chip if you are transplanting it from a BMW non-remote key...or if you are creating an unofficial remote using aftermarket equipment/software like an AK90. :)

But no BMW original/official diamond shaped remote key comes with a loose transponder like in your pic above. :)

My key like the example with the transponder chip soldered to the PCB.

Regardless if powered from antenna or charging coil, if soldered it can have a bad solder joint. Re flow the solder and bring back to life


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