C4 Picasso shuts down when I slow down [automatic 2.0hdi]

[nicolla]

Like the subject of my topic said. It all started now in the evening.
It was working like always, with no signs of anything bad. And it just suddenly started shutting down when I was at the traffic light.
No matter if I am in D, R, or M, it shuts down. In P it works fine until I change the gear to anything (R, D, or M), then it shuts down.

But if I press the gas pedal at the same moment I put it In D it starts going okay as regular, shifting gears as usual (though I noticed it goes in 4th gear pretty early, maybe at 35km/h), until the moment I decide to slow down.
I'm starting to be desperate with the car, even though I love it.
3 days ago it broke the thermostat housing and I had to replace both the thermostat and the housing.
I just can't deal with it anymore. Can someone help me? I'll call the mechanics in the morning, I just wanted to know what are the possible problems.

[EM1996]

To me, this appears to be a bsi error. I had a similar problem with a C4 last year; it wasn't properly shutting off when the key was turned off.
You can alternatively unplug and reconnect the battery for roughly 30 seconds. It will restart from scratch. However, you will have had to reset the time and date on the display, but everything else should be fine - radio stations, display, and so on.

[nicolla]

Turned out it's a torque converter if anyone interested about this. Refurbishment and gearbox service will cost me total around 500eur. So, that's it