Why is water getting into the engine ECU. On my Citroen C3 1.1

Question edited for clarity.

The only way to diagnose strange things like that is to get an auto electrician to look at it. His pro grade scan tool computer can diagnose the functions of the ECU and all electronics.. New ECU need programming on the vehicle when they are replaced.

https://www.google.com/search?q=auto+electrician+near+me

It's possible that the ECU (Engine Control Unit) may have been damaged when you switched the battery terminals on your Citroen Xsara Picasso, but it's also possible that the issue is related to the configuration of the ECU.
The P1613 error code typically indicates a fault in the configuration of the ECU, which can be caused by a variety of factors, including a dead battery, a faulty ECU, or improper programming.
Before replacing the ECU, it's a good idea to try resetting the ECU to its default settings. Here are the steps to follow:

1. Disconnect the battery and wait for at least 30 minutes.
2. Reconnect the battery and turn on the ignition.
3. Wait for a few minutes before starting the engine.

If resetting the ECU does not resolve the issue, then it's possible that the ECU has been damaged and may need to be replaced. However, it's important to have the issue diagnosed by a qualified mechanic before replacing the ECU, as there may be other factors that are contributing to the problem.
If you do need to replace the ECU, it's important to ensure that the new ECU is properly programmed for your specific vehicle, as failure to do so can cause further issues with the vehicle's performance. A qualified mechanic or dealership should be able to assist with the replacement and programming of the ECU.

check for a faulty fuel pressure regulator

the fuel is constantly rotating round the fuel lines, the fuel is pressurized, so any fuel that is not used by the injectors is sent back to the tank.. this give a constant flow and pressure to the tank. the pressure in the tank is regulated by the pressure relay that lets air into the tank to lower the pressure. this is regulated by the ecu and your speed. if the pressure drops or is to high in the tank the engine can cut out on the fuel rail there is a fuel pressure regulator this keeps pressure on the fuel line coming into the injection system. some systems have duel line feeds from the tank for 2 rail systems, this system was not reliable due to the amount of feed pressure needed to fuel 2 lines. and can cause pressure leaks. some systems have a pressure regulator controlled by the ecu on the return line, this is more fuel efficient as it keeps the fuel at a steadier flow back to the tank and give a better fuel spray into the engine. hope this help you.

change the wiper motor relay

could be a faulty wiper on /off switch

knackerd battery can give same symtoms

start with a fully charged battery.....check all earths are good.

cheers

1324

Engine ECU is located in the engine bay, on the driver side(RHD). Body electrical has no ECU (earlier models). Citroen Berlingo uses what is called 'Multifunction Control Modules'. It has 2 of them. One is located in the steering column switch assembly and the other is incorporated inside/underneath the fuse/relay frame in the engine bay. If your Xantia is late model, it may adopt the Berlingo system but I have not seen one that does.

I don't understand what you are asking, please clarify.

If the pressure is up the pump will not cut in anyway! slacken off a fuel line to the injectors a little and drain a few cc of fuel out (it will evaporate fast) then try again, if the pump runs for a couple of seconds then look at the spark, if it doesnot the relay is above the fuses.