Fiat Coupe Club UK

Broken Immobiliser?

Posted By: JPS

Broken Immobiliser? - 01/02/2023 01:55

Hi I've recently acquired a 1995 16v non turbo and it wont start with any of the 3 keys I have but (does crank over),
I tried the battery fix but I believe the immobiliser is completely screwed.
In the owners handbook it says to start the emergency start procedure wait for injector light to come on and pretty much it doesn't come on at all, did have a look to see if it was the bulb but no it was fine
I've scrolled though the forum to see if i could find the answer but came up short.

I would greatly appreciate if someone help/point me in the right direction as id like to remove the immobiliser permanently
Posted By: Edinburgh

Re: Broken Immobiliser? - 01/02/2023 08:34

Welcome to the forum JPS, I'm sure there will be a few rare 16v owners on here who will be glad to see you.

Not forgetting a certain broomy 16vt owner nearby of course.. wink
Posted By: 386ka

Re: Broken Immobiliser? - 01/02/2023 10:18

Hey JPS, nice to see another 16v around. Do you see the yellow CODE light come up? Does it go off?

If the injector light does not come on, I think you might be having issue with the power to the ECU. As far as I remember, if you have issues with the immobilizer, both the CODE light and injector light stay on.
Posted By: JPS

Re: Broken Immobiliser? - 01/02/2023 13:20

Hey 386ka I haven't seen another 16v driving about in quite some time their quite rare these days
Well the CODE light stays on and the injector light doesn't come on at all, I was told by the pervious owner that it was parked up for 6 months and she went to start it and nothing would happen and it sat there for the next 5 years,
so it could also be an ECU issue
Posted By: 386ka

Re: Broken Immobiliser? - 01/02/2023 14:00

Okay - maybe check if the ECU diagnostics plug is connected. If it is open, then you won't see the injector light on ignition.

It is a 3 pin plug, located on the driver side suspension turret or washer bottle. You need to have it connected in order for the light to work. It would not make any difference relating the no-start issue if it is connected - but at least it will give the indication that the ECU is powered, and then we can look at the CODE light.

The thing is that these models AFAIK suffer from being left with low battery voltage, which will affect the immobilizer box and it would need to be reprogrammed.
Posted By: JPS

Re: Broken Immobiliser? - 05/02/2023 23:11

Well after seeing if it was just a plug not done up correctly I came up short, I went over the whole engine bay checking if all the connectors where done up/connected and still no fire only spin
So I think its time to get the ecu immobiliser and key reprogramed But I don't know who to go to for this
Posted By: DaveG

Re: Broken Immobiliser? - 05/02/2023 23:29

You might want to try GrahamL on the Forum, he has fixed my corrupted CODE box (20vt) and it might be similar for 16v
Posted By: Anonymous

Re: Broken Immobiliser? - 06/02/2023 01:25

The 16v ECU stores the immobiliser codes differently so not sure I can do anything with it. I had a 16vt firmware image with the immobiliser disabled but unfortunately I never saw a 16v na equivalent. Don't think I ever even saw a dump of the 16v na firmware at all.

However, it sounds more like an ECU problem than an immobiliser problem.

At ignition on the ECU and immobiliser should power up and switch on their respective dash lights. Then they attempt to communicate with each other and confirm that they are connected to the correct partner unit and if so will then switch off their own dash light.

So the fact you have no ECU light but have the code light strongly suggests a problem with the ECU not powering up along with the immobiliser switching on its light as expected but not switching it off as it can't talk to the ECU, again suggesting an ECU rather than immobiliser issue.

I don't know the 16v fuses but on the 20v there's en EFI maxi fuse for the ECU so check for something similar, or possibly broken wiring or bad connection on main ECU plug.
Posted By: barnacle

Re: Broken Immobiliser? - 07/06/2023 12:34

It's been a long time since I've looked at this, but I have a vague memory that on the 16 - differently from the 20 - the key talks to the immobiliser which authorises it, and then tells the ECU that it's ok to work. So it needs only the key and the immobiliser box to match. But as I said, it's been a long time... one place to look is perhaps the coil around the ignition key barrel and its wiring; check that its close to a short circuit (just a few ohms) from the plug end. If that goes open circuit, I think that throws an immobiliser error - and it certainly can't read the chip in the key.

I too have seen both immobiliser and non-immobiliser versions of the 16VT ecu, but not the 16NA. I have seen a 16NA code dump but I believe at the time I concluded that it was broken; I'll probably be pulling a dump from my 16NA once it's in my hands again (I have concerns about the longevity of the PROM/EPROM/EEPROM in there... we're already over twice the expected lifetime for an EPROM).

Neil
Posted By: PeteP

Re: Broken Immobiliser? - 05/07/2023 13:53

Neil, it was actually a dead 15?amp fuse but I forget where James said it was. Near the battery I think, anyway so no power going to the immobiliser.
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