Can anyone help me find an "I Button" for a NA 1.8iS 1994 immobiliser

Technical Area Electrics & ICE
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  1. My model of MX-5 is: NA 1.8iS - 1994
  2. I’m based near: Exeter
  3. I’m looking for technical help or recommendations on: Dallas Immobilier button

Our MX5 was stored in a relative’s garage for 8 years. It’s now back up and running but we only have one of the little button things that you put on the dash to disarm the immobiliser. It looks like a watch battery on a black fob - you put it on the disc on the dash for a second, it does a long beep and the LED goes green then you’re good to go.

I looked on here and saw that 12 years ago “RS Components” do them. Contacted them and got an email back saying they don’t do car parts.

These I Buttons seem to be all over eBay but they open pub tills and the like. Are these the same as what I need for the MX-5? Can anyone guide me to a source because if we lose the one we’ve got, we’re dans le merde?

All the best
Joe

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When you do find one, it will need programming or your one cloned. If you are passing a Timpson shoe repair place, pop in and ask. They can clone some car key fobs. They may be able to help or point you in the right direction.

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My slightly later UK 1.8 had it built into the key (RFID, static code) but it was almost certainly the same technology. Timpsons cloned it with no problem at all in a matter of minutes.

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That’s cool. Thank you.

My understanding is that to programme it I need to get a blank one, start the car, offer it up to the receiver on the dash and wait for the beep and it’s done. Would Timpsons therefore require the car? My issue is that the car is banged up in our garage at the moment where it’s been for the last 8 weeks and we’re not allowed to use it while the DVLA drag their feet registering it back onto UK plates. I’ll certainly head there when we’re allowed to use it though (if they ever pull their fingers out).

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Thanks for this…so does this mean they can just copy the key without needing the car? I’ll get down there asap if I can!

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The programming you’ve described is different to the way mine worked (the car couldn’t programme new keys by itself) so it may be a case of buying a blank one instead - I’m still fairly sure they could help. With my key, they just dropped it in a kind of little bucket, which was a code reader, then cut the key and loaded it with the same code as the old one. Nowadays, cars have at least rolling keys, or cryptographic challenge/response codes, but it was simpler in the 90s!

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I have what sounds like the same immobiliser on my 1996 NA. The point you raise about it failing or getting lost is a good one. Would love to know if you find somewhere that can provide a solution to this.

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Following, would also like another. Let me know where you source one, good luck.

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I’ve just bought a couple of these off eBay for around a fiver and will see how they go.

For those with the same set up as our MX-5, in theory, you get a blank one, turn on the ignition, offer it up to the receiver, wait for the bleep and the green light and it sucks the right codes out of the car into itself and will work from then on. “In theory”.

However, things I learned looking into this…you probably need a “read/write” one, not a “read only” so that it can magically suck the codes out of the car. Also, they appear to have about a 10 year capacity to remember things.

I’ll report back.

Small rant here…Ignore if you want…I’m kind of peed off that after having the car since 2003 and keeping two keys PLUS the valet parking key and two of these iButtons…it was in storage in the in-laws garage (they offered as they don’t have a car and don’t drive and DO have an empty garage) and FIL collects keyrings (I know, right?) and “didn’t like” the one OUR car keys were on so he took the key off it and just threw it in the bin! I mean, FFS. He’s lovely and everything but grrrrrr. Sorry, I feel better now.

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Meant to mention earlier. I bought a Cat C Micra for my son to learn to drive in and it only came with one key. The immobiliser chip (like a pet chip) was in the key fob and removable. I stuck the chip in the cowling by the key with strong glue and had a couple of extra keys cut with no chip.

Wasn’t worried about it being “mobilised” all the time, it cost £500 and was being kept for no more than a year. It was passed down via nephew/niece for the same use and eventually given away to someone in need of a runabout.

You could probably do the same if you cannot get a spare working and maybe fit a fuel pump switch somewhere hidden.

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In theory if they are compatible registering them is simple, I don’t think that you even need to turn the ignition on, offer up a good one, wait for beep then offer up new one and wait for beep.

I assume that you’ve already searched “ibutton” on this forum, a few potentially useful topics come back

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Hi all,

In terms of the Dallas iButtons I have a fair bit of information…

The good news is that yes you can get the right touch keys if you know what you are looking for and that provided you have an existing button they should be easy to code to the car (but a lot more difficult if you dont…) I’ll tell you know what I know in terms of the system so you’ll know for reference and then you can decide what to do.

It sounds like you’ve got the same immobiliser as me (mine is a late '94 1.8iS first registered in Feb 1995) so the info I have that is specific to the system fitted to my car (which is the standard Dallas touchkey immobiliser using the small round button type affair) should be equally applicable to yours.

I’ve historically had problems with touch keys so have ended up doing a fair bit of research. My car, whilst bought from a dealer in 1998, came with two extra touch keys that didn’t work (although I didn’t realise this when I got it and only noticed a few years later). Anyhow once I’d realised I only had one working touch key I started doing a bit of digging about on the system that had been installed. I also had the car stripped by a local alarm installer (who incidentally could not find out how to do the re-programming!). I’ll therefore give you the info that appears relevant so bear with me as what you need may be buried further down.

The immobilisers on MX5’s at that time were apparently not fitted as standard on the production line in Japan but were fitted by Mazda UK when they imported the cars, prior to distribution. The immobiliser is one manufactured by CEL in the republic of Ireland who have since gone out of business but at one stage product support was being provided by Cobra. As I understand it the immobiliser was originally listed as Thatcham Category 2 and this standing should still apply for insurance purposes, even though it has since been removed from the Thatcham list (because CEL are no longer trading). As you know it operates off a small touch key 16mm in diameter that looks like a lithium battery. The immobiliser is disabled by touching this key against a receptor mounted on the lower section of the dashboard to the right of the steering wheel. The main control unit is remote from the touchkey receptor (in my case this is mounted on the front footwell bulkhead behind the heater fan under a rivitted steel protection plate) and it enables automatically via a time delay, the status being indicated via an LED on the centre console and a buzzer mounted behind.

The whole system works off standard Dallas Maxim (now Analogue Devices) touch key technology which is still available and has millions of combinations of codes. The transponder technology within them allows millions of fobs to be produced but each one has a totally unique number and as far as I know they cannot be reprogrammed… it’s the controller in the car that is reprogrammed to recognise the fob! The equipment used to be available from good electronic components stores such as Maplin or RS but they no longer appear to stock it. It is still being made though and is available, although it’s now marketed as “iButton” technology for security systems and data logging. If you need replacement keys they are available (Selection Table for iButton Devices and Accessories | Parametric Search | Analog Devices)) or more recently the likes of Farnell. The item you need is the DS1990A-F3 product code (although I also have a DS1990A-C8F that also works OK and I believe the DS1990A-F5 should also be OK) which is an ID-only button and should cost about £3 plus shipping. The item numbers are etched onto the button case (in really small letters). Alternatively you could call the Analogue Devices UK distributor Mouser.co,uk to see if they can help. I know one or two people that I have helped in the past contacted Dallas / Maxim regarding the buttons and they were put through to the technical team who sent 2 fobs as a “sample”! The touchkey holders and fobs should also be available from the same places.

In terms of programming, the information I got came from Cobra who I believe took over from CEL, the original suppliers of the immobiliser system, and was slightly misleading as they seem to indicate the need to enter a PIN number, which I found wasn’t necessary as I had at least one touchkey that worked.

From memory the best way to programme a new button, provided you have an old one was as follows:

  1. Switch the ignition on and off to the second position three times in quick succession (in less than seven seconds)

  2. Switch the ignition back on again (the immobiliser may beep at this point)

  3. Then touch the working iButton onto the receptor, followed by the new button (again lots of long beeps)

  4. Turn the ignition off

  5. Leave it a few seconds for the system to reset and then try the buttons one by one and they should be OK.

If you have more than one button just repeat the above process for each new one.

I’m guessing yours should be the same.

OK I think that’s about it from memory but if you need any more info let me know and I’ll see what I can do.

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This is amazing. Thank you ever so much for taking the time out to create this post.

My two iButtons turned up yesterday so I’ll give them a go as soon as I get a chance. If this works on our one, I’ll be delighted!

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No worries - let me know how you get on as it’s a long time since I last helped someone out re this so it would be good to know if I’ve remembered stuff correctly!

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Garfield

Thank you SO much! Spot on! I now have two new working I Buttons. There’s no way I’d have got them working without your instructions.
You’re right too, there’s a heck of a lot of beeping from the immobiliser during the process.

All I’d add is to ensure you buy “Read AND WRITE” buttons as some are read only but I think you covered that in your post with the model numbers. The ones I snagged on eBay for around a fiver for two worked perfectly.

Thanks again. Genuinely chuffed to bits that this worked.

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Excellent - chuffed you got it working!