MX5 mk 2.5 immobiliser problem

[nepeak]

First of all I would like to say hi, I will introduce myself properly soon, it's just that the Mazda dealership have my car and I'm feeling a bit helpless!

I have a 2003 mk 2.5 1.6 that has developed the immobiliser warning light, intermittently failing to start.

The Mazda dealership have just phoned to say that I need a new immobiliser unit (which I figured out but they still charged me £100 to tell me!) They said that they can't obtain these anymore.

My question is what would I need to do this myself? If I sourced a used immobiliser what compatibility issues would there be with keys, ECU etc? The Mazda garage said they could reprogramme the keys. If it helps the immobiliser currently fitted is a TRW.

Thanks for any help offered, I love my car to bits and don't want to see her go!

Nathan

[Mazda Mender]

This is something you can fix yourself...there is a guide on the subject needed buddy.
M-m

[drumtochty]

The original immobiliser that is putting the light on is a Lucas unit that is coded to the ecu on your car and also to the keys of the car in that the imobiliser and the ecu between them know what the electronic number is on each key.

That age of car I believe also has a rolling set of codes transmitted from the keys, just to complicate things I believe.

You may well have a further immomobiliser fitted by a previous owner and you say it is a TRW but that is not linked to the light on the dashboard.

You have two options here and I am not an expert so will not say what is best.

One is to change the ecu and Mazda supplied from the factory Lucas immobiliser for a working pair that you get either from Autolink or http://www.mx5bitz.co.uk.

Then either get

1) Mazda to teach your existing keys to the secondhand replacement ecu / imobiliser set or.

2) You get a steering lock and set of keys from the donor car when you buy the ECU and immobiliser second hand from a vendor and refit the steering lock.

I will not try to guess what is the best option here and will leave that to those who have done a late Mk2.5. I know how to do the Mk2.

[nepeak]

Hi

Thanks for your help. According to Mazda and what I have seen behind the steering columb the only immobiliser that is fitted is the TRW one. Where else should I look for the Lucas one?

I have been in contact with someone who, if I find a matching immobiliser, can then re programme my ECU to work with my replacement immobiliser.

Another puzzling issue was that my car still cranks even when the immobiliser isn't working but when I disconnect the immobiliser it won't crank at all

Puzzled!

[Mazda Mender]

Electrical faults do there own thing they are never straight forward ...if your mazda is a uk spec then she as a Lucas immobiliser box.
M-m

[nepeak]

This is the same immobiliser that I have

http://www.autolinkmx5.com/ecu-b6mv-with-immobiliser-set-mazda-mx-5-mk25-16-7992-p.asp

This was also taken from a 1.6 mk 2.5, is it possible these had this instead of the Lucas?

[drumtochty]

It may well be that the Mazda garage mechanic was not that well versed in the Mk2.5 cars, they are 15 years old now, maybe not.

The Lucas Immobiliser does not stop the starter cranking if I remerber, It stops the car starting.

The after market immobiliser I'm sure is stopping it cranking but I have been wrong before with the Mk2.5 cars

[nepeak]

Hi

Thanks for all the help, much appreciated. This morning I removed the cover underneath the steering rack. The immobiliser that is attached to the "blade" that is hanging down (took a bit of effort to pull off) is the TRW one, for the life of me I can't find another. Next job is to get the ECU number and maybe get one of those "Demobiliser" sets that mx5bitz sells.

Thanks again for the help

Nathan

[psychotic madman]

I hsd this problem a few months ago. Car wouldnt even turn over unless i disconnected the battery, then when the key was removed it wouldnt turn over again. I resolved this problem by removing the ecu and immobiliser and cracking them both open (be very careful with the immobiliser), sprayed them both with wd40 and left to dry for a day. Put them both back on the car and she was fine, and still is, no more immobiliser problems. I am not saying this is the way to go with this problem, but it worked for me.

[Mazda Mender]

Please read this link...

viewtopic.php?f=128&t=2938

There are planty of Nk2.5's being broken for spares out there, so do not limit yourself to just a few Co's, the bay of e as helped me out in the past on this issue, Autolink, suffolk mazda, CBS autos, doctor mx5, etc etc, there are loads out there, we need the ECU number, the large digits .
M-m