Citroen Xsara Picasso SX TOP issue

[SLC 21]

Hello, as I told you in my presentation post, I tell you that I have a Citroen I can start it by feeding direct ac+ from battery to the fuel pump and engine ECU.
I have the schematic of the vehicle but I can't understand it well.
On the other hand, I tell you that I already replaced the BSM B3 first and then the engine ECU + BSI + key chip assembly and the situation remains the same as at the beginning.
Greetings and I hope you can help me.

Santiago.

[GiveMeABreak]

Please describe your issue here, as not everyone reads the introductions.

Please be as clear as possible as to what the problem was, along with any fault codes you have. We really need fault codes here to advise, so if you don't have any that's the first thing you need to do as we can't help without these. Have a full diagnostic (preferably with a Lexia kit) and put any codes here along with your VIN. Please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff.

[SLC 21]

I took the engine and transmission out of the car to make some repairs and a short circuit occurred, the fault that marked me with an autel was 0504 (In the description of the fault it says that there is no communication between the BSI and the engine management control), which is related to the brake pedal bulb, but I can't find what relationship this may have with it. the car doesn't start. What I could see is that fuse 2 and 4 of the BSM do not receive AC+ so the car does not start. As I told you, I first replaced the BSM and then replaced the engine ECU + BSI + key chip and the failure continues.
the VIN is VF7**************[VIN obfuscated, can be read by forum staff].
I understand that inside the BSM is the injection relay that manages the AC+ of the engine ECU (BSM fuse 4) and the gasoline pump (BSM fuse 2) is not working and that is why these fuses They don't have AC+
Greetings.

Santiago

[GiveMeABreak]

That should be P0504. There can be multiple fault P0504 codes, and there should be another 2 digits on the end to get more info, but basically I would suggest you replace the brake pedal switch. This is the most common problem where this fault is active.

[SLC 21]

Please describe your issue here, as not everyone reads the introductions.

Please be as clear as possible as to what the problem was, along with any fault codes you have. We really need fault codes here to advise, so if you don't have any that's the first thing you need to do as we can't help without these. Have a full diagnostic (preferably with a Lexia kit) and put any codes here along with your VIN. Please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff.

Could it be that the brake pedal bulb is causing the car not to start?

[GiveMeABreak]

Highly unlikely.

For non-starting issues, it may be the remote fobs need reinitialising (especially if the battery has been disconnected without following the BSI Reset / Battery Disconnect / Reconnect Procedure.

This procedure also shows the reinitialisation steps if you want to try that - or the complete reset - up to you.

The other thing that comes to mind that are well know with the Xsara Picassos is the ignition module on the steering wheel. If multiple keys are carried on a keychain with the fob used to start the vehicle, the constant weight and rocking with driving can weaken the barrel assembly and it can become loose, which can then affect the contacts inside.

Do you have any issues with the internal blower fan working intermittently? This can also be a symptom of the faulty ignition switch.

[SLC 21]

No, the only problem I have is that the car does not start, but if I apply AC+ to pin 11 and 14 of the gray BSM connector, the car starts without problems.
That is why I would like to know how to read the electrical diagram, which I have achieved. More than anything I am interested in the part of the 3 microrelays mounted on the BSM.

Santiago

[GiveMeABreak]

These modules are not intended to be repaired, but replaced. As such, there's no real detail of the internals of these available, sorry.