Swapping/changing ECU's

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My Name: Ozvtr

Posts: 1079
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 47 times
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I'm sorry, this post is long, wordy and really just for the geeks.
This project is to see how easy/hard it is to replace the critical ECUs in the C3. Outright and not repair/reprogram them. Since then I have purchased a wrecker C3 to salvage parts. So this whole effort has become redundant (%@#$). But like the dead cat...I'm curious!

Say your BSI or engine ECU needs to be replaced, how easy or hard is it going to be? There is theory and then there is practice...
There was a cheap engine ECU and BSI from a C2 on Ebay in the UK. Yes a C2, will that be a problem? let's find out. I asked the seller if he had the keys and the security card for the engine ECU and he said he did. Including postage out to Australia it was a little over 50 pound. I got an instrument cluster cheap from Lithuania. I'm always trawling Ebay for bargains. Why did I need an instrument cluster? Well I'll get to that in a minute. The cost of parts for European cars here is F$#@&d. It's far cheaper to get them from overseas, even including post!!
Initial I was just going to get an engine ECU but this seller was offering the engine ECU and BSI for a cheap price and he had the PIN card for the engine ECU. What's the PIN card? Again, I'll get to that in a minute.
All up i didn't think the total price was too expensive for a science experiment! :lol:
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In case you don't know, You cant just replace some ECUs. Have a look at my post on the security system of the Citroen C3 to find out why.
Just quickly, the engine ECU has a security PIN code. The ECU will only accept up to 5 keys (transponder chips). The BSI retains the VIN code, engine PIN and the Odometer reading. The instrument cluster also has the odometer reading but the cluster and the BSI talk and retain the HIGHEST reading if you change either!! The stock radio beeps if it's VIN and the BSI VIN don't match. Inside the key are components "paired" to the BSI and engine ECU. OK? Got it?
I didn't want to screw up the ECUs already in my car so I replaced only the critical ones. The steering, coms2000(indicator stalks), the fuse box in the engine bay and ABS ECUs are not affected by this silliness and can be replaced with a minimum of fuss.
Why don't I just experiment on what is in the car? 1) that's too easy...I know it works. 2) I don't want to F@#k it up...it's working fine. 3) I don't have the engine ECU PIN code. one of the helpful previous owners threw away the PIN card! So I cant code in new keys.
Fundamentally the Citroen C2 and C3 are the same but apart from model configurations, there are a few differences. The C2 is a two door and the C3 is a 4 door With 'child locks' on the dash. The tailgate is different, but electrically I don't think it matters. C2s don't have a sun roof option. You also have different model variants in both cars, like air con and manual windows. Will these things make a difference?
In the Citroen parts catalogue, when you look up an ECU it may say "and part to be configured" or it may give you optional part numbers for configured or unconfigured parts. What does this mean? Well the ECU can be configured by the factory or configured by a technician when it's fitted to the car. But I'm about to find out that some configurations can not be changed!
Configure what? Well, the ECU may need to know what your car does or doesn't have as facilities. For example the BSI may need to know where the speed information is coming from? From the ABS system or a sensor on the gear box. The engine ECU might need to know if air conditioning is fitted and if it's climate controlled or basic. Stuff like that...and there is a lot of stuff!
How do they know what is needed to configure the ECU at the ECU factory for your car? You will need to supply your VIN if that ECU needs to be configured.
For example the engine ECU PIN is configured into the BSI in the factory (the BSI factory), it can not be configured by the LEXIA when installed in the car!!!
But the question is how PHYSICALLY different are these ECUs from each other? What I mean is like ECUs from one car compared to it's counterpart on another car. So like ECUs for like ECUs. Are they all the same but just configured differently or are there physical differences limiting what they can and cant do? There are a whole bunch of numbers printed on the ECUs in my possession and I have no idea what they mean. There were at least one set of numbers on each ECU that matched my old ECUs so I hoped that was a good sign.
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The first thing was to fire up the LEXIA and see what the settings for each of the relevant ECUs already in the car were. I took pictures of all the menus on the LEXIA screen...I thought! Unfortunately I failed to scroll down on some pages and I missed some menus altogether. :(
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This is just some of the screens.

Now, I have skipped menial things (in the text) like disconnecting the battery and waiting for system reset, but I did do them. You shouldn't just disconnect the battery. There is a process.

I disconnected the old ECUs and plugged in the 'new' ecus.
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The Odometer reading of either the Ebay C2 or what was in the Cluster. (I'll never know!)
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Fired the system up. Of Course things were a bit wrong. The auto air conditioning was acting weird and the radiator fan ran continuously. Hmm.
A scan with the LEXIA shows the donor C2 had no aircon and I couldn't identify the engine ECU. There were also a few other things 'missing'. It must have been a very basic model? (turns out it was a Furio).
Ok, back to the LEXIA and started with the BSI. This is the fuse box in the glove box and is basically the brains of the car. I go through the menus and sub menus telling the BSI what the car does and doesn't have, effectively copying the settings from the 'old' BSI. However the menus aren't exactly the same? That doesn't make a lot of sense. Are the options coming from the LEXIA or the BSI? As I went along changing the configuration new menus popped up and some old menus disappeared or changed. the list of menus began to look more like the 'old' menu but I'm not sure, there are a lot of menus!!
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Next you have to save the settings by hitting the 'configure' button. WTF!? You need a 5 digit pin to save the settings of the BSI? The pin for the engine ECU is 4 digits and that is not the PIN we need...boy did I try! So off to the interweb and a bit of digging finds the code. It's just a generic number used by PSA technicians. I punched it in...and...it worked!! So the settings are saved. All the relevant ECUS now pop up in the 'global' test.
The engine ECU communicates with the LEXIA but it wont identify itself. Very strange as both ECUs are SAGEM S2000PM1's controlling KFV engines and this ECU has already been installed with this BSI in a C2. Huh? I can nominate the ECU I have installed from a list provided by the LEXIA but LEXIA says that it only has an option for the 16 valve version!? No 8 valve option. So the options are "the unidentified ECU" or a 16valve version? Also in the engine submenus there is no option for an automatic gearbox, only 'long' or 'short' gearbox!? I set every thing up as well as I can but the radiator fan still runs flat out. I disconnect the small grey connector on the radiator fan shroud to stop the fan from running. After re configuring the BSI and engine ECU a few times the fan stops running all the time and responds to the 'actuator test' correctly.
I configure the engine ECU as best as I can and decide to see if the engine will run. This tests the key and the engine ECU. Oh, by the way I had to swap over the key blade from the old key to the 'new' key. This meant I was using the 'new' transponder and remote but, as expected, they worked fine. In fact I coded in a brand new transponder chip just for shits and giggles, after all, I had the PIN code card (and it worked).
This could go horribly wrong but what-the-hell! So I turn the key and turn the engine over. It takes a bit to start and it pops and farts but it starts to run smoothly after a while. Idle is a bit high but running OK.
So the engine ECU will run the engine but after turning the engine off there are a raft of ECU faults.
Basically the faults boil down to the engine ECU not talking to the gearbox ECU. HMM. I fiddled around a bit but this was the best I could get.

OK so what did I learn?

Well...this experiment was a bit of a failure. If my car had a manual transmission however it would have been a success but lets have a look at the autopsy shall we?

The BSI: apparently there are 3 levels of appointment for BSIs. Down market, mid market and up market. The BSI I got was out of a Furio. I would have assumed it was a down market model but everything seems to work as advertised and I managed to configure it the same as the one that was in the C3 originally, including 4 door locking, auto lights and auto air con!? Both BSI's were F0-00 part numbers. So I would chose a BSI with the same appointment level and/or part number if you ever needed to or just get a F0-00 it should do everything. The big trap is the OLD PIN number in the BSI for the current engine ECU. Apparently, Citroen will give you the PIN code (only to YOUR car)...for a price. You may or may not have to identify yourself as the owner of the car.
LEXIA does not have the ability to change the PIN code already in the BSI. You need to "hack" the BSI's EEPROM (it's memory) to change the pin code!

The Instrument cluster: Well this is the least bothersome of the lot. I only got this one so I didn't stuff up my odometer reading by swapping out the BSI. I guess I could just have disconnected the old cluster but the theory was that I was going to drive the car...on the road...with the 'new' ECU's installed. So it might be handy the know what speed I was doing! However, one thing that is apparently different is the number of warning lights on the cluster. For example there is no pre-heater lamp for a petrol engine but there is one on some diesels! Again, the BSI and the cluster will conspire to change the mileage to the HIGHEST if you mix the BSI and cluster from different cars. So if possible get a cluster with the same or less mileage. But if you are desperate your old cluster will work, you just risk increasing the mileage.

The engine ECU: OH BOY!!! The engine ECUs are 'HARD' coded for marque and model. So a Citroen c2 ECU is supposed to be in a Citroen C2 and nothing else. Not a C3 or a Peugeot 206 or a Berlingo! Now it will work but you will need to 'manually' configure the ECU and tell LEXIA what it is. Why? What difference does it make? I don't know! When you start the LEXIA session, it identifies the car automatically or you can 'tell' it what car you are working on. If I tell LEXIA we are working on a C2, it identifies the C2 ECU but not if I install the C3 ECU and vice versa. Also if I went into Peugeot Planet (Peugeot's version of LEXIA) it would not identify the ECU either.
Manual or auto or piloted auto!? If your car is a manual the engine ECU wont talk to the gearbox ECU (for an auto or piloted manual). Also there is an option for a 'long' and 'short' gearbox in the manual configuration!!?? I assume they are talking about gear ratios?
Auto box. If you have an auto or piloted manual gearbox, for various reasons, the engine ECU and 'auto' need to talk to each other. For example in the sensodrive set up the throttle needs to be backed off during gear changes.
So if I have a C3 auto with a 1.4i engine, it requires an engine ECU for that engine (say, 1.4l 8 valve or 16 valve petrol), marque (Citroen), model(C3) and gearbox type(auto) for installation to begin to go smoothly!BUT you can use a different marque (Peugeot) and model (206 i think, or a C2) as long as the engine and gearbox type are the same. The road is a bit more bumpy (so to speak) but it is do-able. You will just need to configure the ECU 'manually'.

Ok, so what is the take-away from this? Well PSA certainly tied this up in a nice neat knot to stop thieves from stealing your car, or did they do it to stop anyone other than the dealers working on your car?

The instrument cluster and BSI turned out to be what was expected. You must have the right type of engine ECU and you need the "matched" BSI and keys!!! If you don't mind the LEXIA whinging, a C2 (equivalent Peugeot ETC) ECU will work but only the right type (manual/auto).

So what's the easiest way to do this? If you have problems with the BSI...repair it!!! Get a BSI from the breakers and swap the broken parts. The engine ECU...Ah boy!! Get it repaired.

Next simplest? Get the BSI, engine ECU and keys from a donor car with the same engine, gearbox and appointments as your car. Swap the guts of the keys and change the VIN in the BSI using a LEXIA.

Do I need to worry about all this sh!t???? ...well...Not really... It seems that the engine ECU's are very reliable and very rarely fail!! The BSI?? Well the relays running stuff like the central locking are crap but they are fairly easy to replace. The instrument cluster? Again they seem reliable.

Stay tuned, in the future I am going to try to reprogram the C2 engine ECU. I believe the hard coding of the gearbox type is in the flash memory. I will try and copy the flash memory or physically move the flash from one ECU to another. You can also read the engine ECU PIN from the 'matched' BSI EEPROM. This is really getting into nerd-burger territory! Another project for the future. I am also going to pull the BSI, engine ECU and instrument cluster out of my wrecker C3 and see how they go in my functional C3!!
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