Want to change the ECU , BSI, everything but I require help

Hi everyone,

My GF has just purchased a 2003 Citroen C3 1.4 Petrol Auto (not sensodrive) and we have a small/big problem.

We bought the car knowing at some point the car had had a 2nd hand ecu fitted. The original key opend the car via plip and key, opened the glovebox and the filler cap but nothing else. The "new key"opend the doors on the romote and started the car.

The original key has been stolen so whoever has it can enter the car whenever but cannot take it. We also cannot fill it with fuel!

I can se the original VIn to get another original key so we can fill it up, but that means the car is not secure. I have been offered a full set of barrel, ecu, bsi (?), door locks, two keys and a filler cap for $470 (I live in Australia) which is okay. BUT nobody is confident that swapping out the whole unit will actually get me a car with working stereo, abs, speedo etc and there are almost sero people who could diagnose it and get it working IF it didn't play nice.

Am I missing an easier solution? Is it easy enough to swap everything over? Anyone done this?

Any advise or help grately appreciated!

Hi ajg

Am I missing an easier solution?

Yes, get a key made that will fit the fuel filler cap, from the VIN as you suggested.

Remove the stolen key from the keys that will work on your car, as you would for any time a key is lost or stolen.

Citroen dealer can do this, but a home DIYer would use lexia. It is just a case of wiping out all the keys stored and adding (possibly the new 'virgin' key and) the existing key to the system. Any keys not present at time of reprogramming will be disabled.


You may not want the new virgin key to do remote unlocking and starting as this is more cost. If you want the new key to only unlock manually you will save money by not having a transponder and remote board and the extra programming, you will just need a blade cut.

Hi Arfur Dent (HHGTTG reference?)

I can get a key made using the VIN which will allow me to open the fuel cap and open the drivers door. This is all it will be able to do. As the ECU was a 2nd hand unit (so I believe) it came with one key and an ignition barrel. That key only works the ignition barrel, starts the car and opens the doors via the remote.

That also means that even if I could remove the code from the BMI the thief could still open the car via the door lock.

Citroen Adelaide have already told me that as the ecu unit is different from the original one I cannot reprogram anything (as the citroen ecu program will be wrong for the new ecu), although I wonder how they got the new ecu and key to work everything....

ajg wrote:That also means that even if I could remove the code from the BSI the thief could still open the car via the door lock.

Which would also set off the alarm.

You could disconnect the drivers door lock, so no key would open it. The only problem I see is if the BSI locks up or the remote unlocker gets out of sync and you need to open the door with the key to reset it by switching on the ignition.

A better solution (with regards to cost and usability) would be to remove the drivers door lock and replace it with a different lock. You would end up needing 3 keys for the car..

1, to manually unlock the drivers door if the remote fails

1 to open the fuel filler

1 to start the car and operate the remote locking.

but..

If you could find a drivers door lock, and a fuel filler cap, with the key you would be back to 2 keys at minimal cost. Any scrap C3s where you are?

ajg wrote:Citroen Adelaide have already told me that as the ecu unit is different from the original one I cannot reprogram anything (as the citroen ecu program will be wrong for the new ecu), although I wonder how they got the new ecu and key to work everything....

Well, I wouldn't take everything they said as fact. I would try connecting lexia myself and dabble to prove to myself what can and can't be done with a replacement BSI/ECU. I don't expect there to be any difference in key programming for an original BSI and a replacement BSI.

ajg wrote:Hi Arfur Dent (HHGTTG reference?)

Ahh, i didn't know it had an alarm system on the car, just an immobiliser.

There is a single scrapper/Citroen specialist who might be able to source a filler cap and door lock. This was my first port of call before Citroen said they cannot remove the old code.

Don't worry, I do not trust a word they say. My GF called them up to get the four digit ECU code using the original VIN number and after "looking it up" while she was on the phonë her car amazingly didn't have one. BUT they could still order a new key and try to program it for her. Hmmmm. Another call by me and we are getting the code and getting a blank cut so it can at least be filled with fuel while I work out a better and more elegent solution.

Thanks for you help Arfur, and don't forget to keep your towel close by at all times

Ahh, i didn't know it had an alarm system on the car, just an immobiliser.

This may be an option in your territory, its easy to test. Remote lock the car, then unlock manually with the key and open the door. This will set off the alarm if its fitted. Silence the alarm by putting the key in the ignition and turning.

Do keep us update on how it goes and which solution you chose.