Key Coding - A Trap For The Unwary
 

A friend called around early this morning with a customers 75 to code a key into its BCU.
Quite frustrated. We tried to enter the two line barcode (as printed on the tag), three times. The screen acknowledged that our encoded input was successful.
However when attempting to lock or unlock the door nothing worked.

In frustration, I delved into my parts box and gave him one of my keys. This time everything worked, and my friend was able to head off to work at the dealership.

A bad key is of no use to me. The barcode tag (dated 08/07/04)looked genuine, but I had not seen an expanded barcode that incorporated a forward slash (/). You will have to excuse my ignorance as I have probably only seen 50 or so 75 / ZT keys.

I decided to check the code slip on the circuit board: it recorded "N3D7643".
Both strings on the barcode slip differed. No wonder the BCU retained its barrier.

The question is, did someone down the line attach the wrong bar code tag to this key? Or is it a case of the operator needing a set of spectacles.

I suspect that when ordering spare keys, dealerships supply the cars VIN through the system to BMW Godolphin. BMW would then be able to identify the cars immobilisers coding from its records. After processing (coding) the immobilise, the key(s) is returned to the "dealership" for entering the coding into the cars BCU.

It dawned on me that is probably why (at least here in OZ) some folk think that you match the transponders details to the immobiliser at the same time that you enter the data via T4 to the cars BCU. Of course Godolphin, holding the immobilisers recordings in its database, simply code the transponder chip to match that already stored in the immobiliser.

I still don't know how a new key could go through the system with a faulty listed barcode.

You can code the remote to the car using TOAF and the number on the circuit board.

Yes you can, but Bruce has a real T4......however the sticker on the key PCB appears to have seven digits rather than six ;)

Bruce, I would suggest you generate the barcode, omitting the "N" prefix ;)

Brian :D

Thank you Brian for your advice. You know that it took sleepless nights and trial and error stabs to get it.
My friend has the use of the dealers T4 and asked to come around as his T4 wasn't working. After trying to install the remote code with my unit, I now understand why he thought his T4 had packed it in.
I may discuss this further as there are a few anomalies with this remote tag.

Meanwhile, here are my figures.

Code on the remote circuit board: 3 D 7 6 4 3

Top string:
Barcode listing: P 3 D 7 6 4 3 3 D 7 6 4 2 F F /
My calculation: N 3 D 7 6 4 4 3 D 7 6 4 3 F F /
Second string:
Barcode listing: F F F F F F F F C 2 8 9 B C 2
My calculation: F F F F F F F F C 2 8 9 B B 1

7th. and 11th. items in top string differ. 14th. & 15th. items in second string differ.

Regards,
Bruce.

It could be the code but I have had a key do exactly the same thing ie when coded the car accepts the key code inside the key but when trying to open the car just won’t work.
Ended up the key circuit board was faulty .

Key Barcode
 

Thanks Brian,

This keys barcode tag commences with a "P" rather than the "N" that I am accustomed to see.
When amending my calculations to incorporate "P" I concur with the printed barcode.
If the barcode tag was NOT attached to the key, how would I know to substitute the normal "N" for this "P". Is there any code reader that can identify the I/Cs programming / coding - so as to identify if a different letter has been incorporated in the coding.

Or if one has a key without the barcode tag, do you just use a trial and error approach, selecting different letters in turn. Does anyone know how many alphabet letters MG Rover / Valeo used?
I had the mistaken belief that, in the barcoding industry, "N" indicated the small sized barcodes. How wrong was I.

Maybe this could be the reason that some garages here in my home city have not been able to code some of the remote keys. And this may be the reason that my friend believed his T4 had failed.

Bruce.

Merry Christmas everyone. We are 1100 hours ahead, and had an enjoyable family gathering.

Frustrated at not finding anything on the net relating to N and P leads to our barcodes.

With nothing to lose, I decided to check the FOB keys frequency. Checked my cars key and it read 433.92MHz - as it should. Then I tested the frequency of the non conforming key. Surprise! Surprise! The frequency meter didn't register - zero. Checked my good key again - to confirm that the meter was working - o.k.
I have never encountered this before - first with a "P" referenced barcode and now finding its frequency is zero. Wonder where the MG owner sourced this key?
Will need to check the circuitry. I do have a few low-loss SAW (surface accoustic wave) 433.92 filters in my parts box. Can anyone please advise me whether SAWs are compatible with our key FOBs.

Compare the "new" PCB with one of your own Bruce, I rather think what you have is a 315 Mhz key ;)

Good isn't it ?

Brian :D

Thank you Brian for mentioning this.
It also crossed my mind, so checked its frequency. Whilst My keys all recorded 433.92MHz, this key registered Zero MHz. In other words the new keys circuit is flawed - it's a dud.
My son-in-law also pointed out that my 433.92 SAW filters are not suited - the crystal on the circuit board will be the frequency controller.
Presume that the crystal is probably a silicon dioxide compound, doped to reduce its frequency to match our system.
Best I bin it and move onto the next problem. At least the battery is salvageable.
Thanks for your comments.

How do one goe about doing this?