E39 Key question

[farrelr3]

Hi all,
Quick question, I bought an ak90 key writer, and I'm trying to get my head around it now. The key I have for my car is a 433 mhz key, with the elmos chip(10030a). I'm trying to produce a key from the ak90, which gives two options for transponders to write a key, 10030a, and pcf7930/35. All of the blank keys I can see online for sale seem to be pcf7935. Can I buy one of these, code it with the pcf7935 option in ak90, and have it work with my ews, even though mine was originally elmos, or can I only use a key that has the elmos transponder chip on it(which I cant find!). Thanks

[JimLev]

There aren't many here that do the key writing.
If you search you should find at least one person on this forum that does it.
If I can think of his name I'll add it later.

[djb2]

The keyless entry frequency (315/433MHz, precisely controlle) is unrelated to the security transponder frequency (designed for 125KHz, but can work at perhaps 100-150KHz). Think of them as two different radios, connected only by the battery charging circuit in the diamond keys.

You probably have a blank PCF7935 transponder. Select that option. I don't know that individuals can buy new ELMOS chips of any type. Those that are 'available' are circuit board pulls or fakes.

[6spd540]

If you're going to use a pcf7935 chip in a dimond key you need to remove the 10030a chip from the PCB (or remove the coil so it doesn't get energized).

Sent from my Pixel XL using Tapatalk

[djb2]

There isn't room for a 'coffin' transponder in a factory diamond key, unless you strip out the circuit board.

Nor much of a point, since it has become much easier to find a keymaker that will cut a $12 aftermarket diamond key, some of which are nearly indistinguishable from factory keys.

[geargrinder]

There isn't room for a 'coffin' transponder in a factory diamond key, unless you strip out the circuit board.

Yeah the aftermarket sellers sell the blanks that come with the coffin-chips, so I guess the remote PCB they use is re-laid out to make space for them...

DJ note he doesn't have a new key yet. He's asking if those aftermarket coffin-chipped keys will work for him... answer is "they should" although always with those eBay copy electronics from Asia things I try to buy from the most reputable seller i can find...

[djb2]

Comment #4 was about removing the 10030 chip to use a PCF7935 transponder. That's not going to physically fit.

I agree on buying the transponders from a reputable source. I bought a 10 useless, badly-molded counterfeits on Alibaba. That's less likely to happen on eBay because of how easy it is to get a refund for a bad product.

As a loosely-related note, I've had better results swapping the original 10030 chip onto a used diamond key board than trying to replace worn-out pushbutton switches. The replacement switches I've found are shorter and not as robust. It's not that difficult to remove an SO-8 chip on the edge of a board, while it's a tight squeeze to remove the middle pushbutton.

[farrelr3]

Thanks very much for the replies guys, ive since bought a key with a pcf7935, and i'll have a go at coding it once it arrives.......My only concern was that it would not be compatible with my ews, but sounds like that wont be an issue. Thanks!

[geargrinder]

As a loosely-related note, I've had better results swapping the original 10030 chip onto a used diamond key board than trying to replace worn-out pushbutton switches. The replacement switches I've found are shorter and not as robust. It's not that difficult to remove an SO-8 chip on the edge of a board, while it's a tight squeeze to remove the middle pushbutton.

Great tip. I've not had to try to revive old keys but that's great info.

[farrelr3]

Got the new virgin key, coded it with the pcf 7935 option, and tried to start engine but no success. Any idea what I'm getting wrong?

[djb2]

What key number did you use? Is that key number enabled in the EWS?

What does the key report when you read it back after trying to use it?

[farrelr3]

I used key 8-which was one of the only free new slots...... when I read the key it comes up with the vin, key number etc

[djb2]

Verify that key number is enabled in the EWS. You can enable and disable keys in INPA. You don't need to hook up the AK90 to do it.

I prefer to use lost low-number keys, which avoids the issue.

[Fx323i]

If the other keys work, I would suspect the position of the transponder to the ring antenna, or you are having two transponders at once near to the antenna.