Technical Lost code card for immobilizer

[douglas_geb]

I've stumbled across this forum while looking for a solution for my problem, maybe you can help me...

I have a Fiat Brava 1.2 16V '99 with an immobilizer system with a master key and code card.
I bought the car 2nd hand, and I received from the previous owner only the red key and 2 blue keys, but no code card.

Some weeks ago my car immobilizer suddenly stopped recognizing the key, and the car refused to start anymore.
The fault appeared out of nowhere: I drove the car 3-4 hours, then stopped for 10 mins, and when I wanted to continue, it didn't recognize the key.
I assumed it was some simple contact problem but it didn't go away.

After trying 100 times I called road assistance and they took the car in some garrage to check it.
The guys said they found and solved some cable problem, but apparently messed up something more because they started asking me for the immobilizer code card.

I don't have the code card, and neither the previous owner, so I had to bring the car to a local Fiat garage.
This turned out not to be the best move:
They didn't even read out the error codes from the ECU or immobilizer, neither they tested the modules one by one to find out where does the sequence
The only solution they proposed was to replace the ECU with a brand new factory one without a code, take out the immobilizer and continue to use it like that.

To me this sounds quite a waste of spare parts and money (the ECU costs almost 20% of the car! value) , because as far as I understand, the ECU and the immobilizer are working OK, but they mismatch with the code, or one of them lost the code, or it's something with the antenna...

The parts are the following:
ECU - Bosch 0261206276
Immo box - Magneti Marelli IMM110.01

Does anyone have a signalling diagram of the code recognition sequence that the key, the immo box and the ECU exchange during startup?
How about electronic schematics of the ECU and immobilizer?

I'm trying to understand how the whole sequence works and to see if I can test some parts myself.

One more question:
The ECU and the immo box are both out of the car.
What happens with the coding, is it still there, or does it get reset?

I would appreciate any details or links, I searched across the whole Internet, but found almost nothing...

Thanks a lot for the help!
Douglas

 

[T14086]

Does anyone have a signalling diagram of the code recognition sequence that the key, the immo box and the ECU exchange during startup?
How about electronic schematics of the ECU and immobilizer?
I'm trying to understand how the whole sequence works and to see if I can test some parts myself.

I would appreciate any details or links, I searched across the whole Internet, but found almost nothing...

Reason why you cant find any info is because this info isn't released(legally)as it would comprimise the security of everyone elses cars! It is contained within dealer manuals and no doubt there are details somewhere!

From what you say I doubt the problem is due to any code card,sounds like more to do with communication wiring between the ECU & code box.

Take it to a garage that will read the codes & monitor the key status on examiner as should of been done.

 

[douglas_geb]

Hi,

thanks for the reply.
The car is already at the Fiat garage and they said they couldn't determine the source of the problem.
I also contacted Fiat directly to find out if they have any test center for the parts, if the local garage does not have a clue, but they are even more fantastic with their customer service, what can I say...

I asked for the signalling sequence because I thought for 600 euros I could buy a diagnostic interface and start looking for the fault myself...

No wonder Fiat gets so many bad marks in the car surveys. I decided to ignore them when I bought the car, I thought it's just the local market does not like Fiats, and it cannot be that bad with any new car, but obviously it can.
Not everybody can handle high tech as the Japanese ;-)
A friend of mine a car mechanic said I can leave the key in the Brava, and still no one would try to steal it, maybe should've sticked to the low quality instead of an electronic immobilizer...

Sorry for the bad words, I know the Brava forum is not really a place to complain, but I really get frustrated when I run into absurd problems...

Any other good ideas except Fiat service would be really helpful.

 

[T14086]

Probably code box is at fault.

Red key is needed to programme system but later Fiat systems use access via examiner with a code card number.

My advice...take to another dealer who can be bothered to read the errors & pull out the immobiliser fault finding manual!

As for Fiat in surveys...your car is 8 years old,buy a 8 year old escort & see how much that will cost you just to get it through a MOT! If we believed all that we read we would be scared of leaving the house let alone get in a car.You have one advantage here,the best car forum on the net,people that will help you often within minutes of posting!
Unless you know the history of the car you do not know what has been done/messed about with by previous owners.How long have you had the car?

 

[douglas_geb]

Probably code box is at fault.

Red key is needed to programme system but later Fiat systems use access via examiner with a code card number.

I thought about that, either the immo box or the antenna...
The problem is (as I was told by the Fiat service), the current code is saved both in the immo box as well as in the ECU.
If you replace it with new immo, you have to replace the ECU, because it has as well the old code.
They said the ECU comes uncoded from the factory, and as soon you attach immo box to it, it get programmed with the code from the immo box, and it can only be used with that box, and no other...

If I understand well what you're saying, I could replace the code box and reprogram the blue keys with the red key, and then the ECU will be as well programmed?

Unless you know the history of the car you do not know what has been done/messed about with by previous owners.How long have you had the car?

I have it 3 years now, and in general I didn't have major problems (until now), but I had two problems so far which I didn't expect from a such new car:
- I had to replace the rear suspension two years ago (the car was 4 years old
!)
- the last two summers, during summer when the weather was warmer, the car began to run very unstable in neutral, and it would very often shut down. I had the car ECU checked in the same service, but they couldn't find anything , and they charged me 400 euros!

I'll look for another service with better electronic competence...

Thanks again for the support!

 

[T14086]

I have changed code boxes without changing ECU's before.