ECU not detected

[Azrael]

I own a Xantia S2 1.8 16v with automatic transmission that has , apparently, immobilizer problems: when you put the key in the immobilizer light starts blinking and the engine doesn't starts. According to my mechanic it's something to do with the ECU since he can't detect it with Lexia. All this was caused probably by me when i plugged and disconnected the battery with the key on - i know, i'm a moron.
Here are my questions:
1 - is there a way to test the ECU to confirm it has failed?
2 - is there a way to reset it?
3 - if the ECU is dead and must be replaced do i have to find and buy an identical replacement (same model - Bosch MP 5.2, for an auto trans model, from the same manufacturing year) or could i get a similar one? If it's the latter then which? Would this
http://www.ebay.co.uk/itm/ws/eBayISAPI. ... 0669334513" onclick="window.open(this.href);return false;
work out?

[citroenxm]

TRY.. disconnecting the battery Again, with the key OUT of the ignition.. Leave it dosconected for about a min or two, then reconnect the battery. Wait another min and try to start.... Its all I would do to start with at least.

[wheeler]

Was everything working fine before the battery was disconnected ? why were you doing this in the first place ? Can all the other ECU's be detected by Lexia ?
Before condeming the ECU you need to confirm it has all it's live feeds & earths.
That set on ebay would be useless without the CPH unit as the ECU, CPH & transponder chip are all a matched set & second hand ones cant be recoded to another car with Lexia. It can only be done by reading & re writing eproms on the circuit boards which is a specialist job.
If you go down the 2nd hand ECU route try to get the VIN or reg of the car it came off incase you need to do any key programming in the future.

[Azrael]

To citroenxm: tried all of that even before taking the car to the shop, in all possible configurations, to no avail

To wheeler: the car got snowed in and the doors have been frozen shut. To get in i had to force them and after that the latch on the driver's door hasn't worked properly and the door sensor has been triggered. That the latch eventually thawed and that has allowed me to drive the car home and lock it. The next day i discovered that the door open warning was still on and the battery was flat. So after returning from work i though to save me the trouble to carry the spare battery to the car thru the huge snow so i disconnected the battery all together. The next day when i tried to start it it all went caca.
My mechanic tells me that all the other ECU's are working - he has been able to pair the key to the system (he tried that first thinking that the bad disconnect has messed up the pairing somehow - so he has obtained the security key). Now he can no longer detect the ECU so i still need to know if it's a faulty ECU (and how to test that), if it's possible to install a sh one, what model (identical or whatever one i can source from a Xantia 1.8) and how that can be done.
BTW where are those live feeds & earths located and how do you test them?

[wheeler]

BTW where are those live feeds & earths located and how do you test them?

They are at the connector of the ECU, you would check them with a multimeter in conjuction with a wiring diagram for that injection system.
If any of these are missing it can stop the ECU powering up which in turm means lexia will not see it. These must be checked before condeming the ECU
Is the door open warning now operating as it should ? believe it or not this can affect the imobiliser operation.

[Azrael]

Yes, the warning is now off - the door latch mechanism has been heated and it now functions correctly.
Unfortunately both i and my mechanic don't have those diagrams - can you point me to where i could get them?

[wheeler]

Yes, the warning is now off - the door latch mechanism has been heated and it now functions correctly.
Unfortunately both i and my mechanic don't have those diagrams - can you point me to where i could get them?

If your mechanic has Autodata he should be able to get them off that, Failing that if you speak nicley to Citrojim & give him your engine code & RP number he might be able to scan them for you.

[Azrael]

I'll get them asap.

[JamesQB]

Auto data has no info for the MP 5.2 system ECU at all, only the Sagem and MP 7.3 systems. Vivid work shop only has Sagem info.

[Diabolical]

I damaged my ECU changing a chip (long story). Same thing not detected even Lexia couldn't find it.

I sent it to ECU Doctor 01752 346437 repaired and back in 7 days £45, was 5 years ago so probably bit more now.

PS: NO CHARGE IF NOT FAULTY.

[Azrael]

Autodata indeed doesn't have the schematics. I went to the local dealer and even it doesn't have it - it appears that my model is extremely rare. FML

I currently live in Romania, i can't send my ECU there since, from what i read on their site, they work exclusively inside UK.
I can't even buy a sh one from Ebay since most sellers there again supply only UK customers