Pejo 207 1.4 hdi stop status

Hello everyone, I wrote in this forum before, pejo 207 1.4 hdi 2009 model car, sometimes when I turn on the vehicle, it stops when I first turn on the ignition and it works as if nothing has happened when I switch the ignition on. When we connect it to the device, it did not cause any malfunction. When it stopped, either exhaust emission failure or oil pressure fault warning writes. When the vehicle stopped, when I connected the ignition to the device immediately without turning it on, we saw that there was no connection with the U1108 engine computer and the U1308 engine computer gave a malfunction. We tried the different 207 brain and used it in that way and we saw that the vehicle stopped again. It was said that there was no abnormal thing in the fuse box. The masters said that there was no mechanical problem, it was an electrical problem, the instant the vehicle stopped because the communication with the brain was interrupted, and I saw that 3 5 more friends lived and could not find a solution. What is it, does anyone fix this problem?

The catalyst downstream oxygen sensor may be faulty.

I think there may be a short circuit in the electrical installation. I also say that the electrical chassis connections of the vehicle have been cleaned and checked.