Ive got a 1999 Ford Focus Zetec 1.8TDDi which i'm wanting to program another key to the ECU.

Now I've been told and read that I need two keys coded to the ECU before you can program one yourself, and to get a second one coded will set me back about £150 via Fords (as they have to wipe the keys off the ECU, then reprogram the original plus the "second" one back to it)

Here's where I have uncertainties. The Focus had an engine swap (along with the matching ecu and immobiliser part of the key) a few years ago. I was supplied with two keys, one three button type and one with the "blue" pats chip in the top.

The locks on my Focus remained the same so we pulled the "new" button key apart and reconnected the existing blade to the new buttons.

I've been using that for the last 3/4 years but now I'm thinking I need another key cut incase something happens.

If you remember I said I had another key with the blue chip but after checking online it's evident that in 99% of the times the glass pats bit under the plastic breaks when you try and remove it so that's off the cards.

I'm unsure of the sequence I have to do to program a key to the ECU but id imagine you would need to present each key and follow a specific sequence before adding a new key?

Here's where I'm seeking help. Can I not split the button key again therefore I'd have the blade and the pats (button part) of the key, then insert the blade and hold the pats part next to the key, do the sequence, then remove both the blade and the pats/button part. That's key #1 done.

Then im thinking to insert the blade AGAIN but this time place the complete blue chip key next to it (as that has the blade from the doner focus so cant use the blade) and follow the sequence again? That would be key #2 done?

Once that's done I can present the new key and do the final sequence and away I go? As long as the blade has been cut obviously.

Hopefully someone can shed some light and thank you for reading/your responses in advance.