Okay. That code is telling you that some other module like the transmission controller or ABS or drivetrain control module (4WD) was not able to communicate with the PCM when it needed to. So it is not going to name it in the title of the code. It is going to be in the scan tool that says something like ABS - U0100- PCM/ECM "A" lost communication. This means the ABS is what lost communication with the PCM. However, your tool may not give this level of detail at which point we should ignore it.
If this code is active when this happens then the module that set the code against the PCM would be the issue. However, if it is stored and it not there each time it stalls then it is not related or at least not causing the stall.
That means we have a rough idle and stall with no codes. That means we most likely have a based engine issue. So does your scan tool monitor the o2 sensor data?
If so, what does it read while you are driving and when it stalls?
I am concerned with either the short term fuel trims or o2 sensor voltages. They are not the easiest to watch when driving so either have someone else drive or just set your phone up to record about 15-20 second video when it is idling rough and then what it does if you can catch it stalling.
However, I think we need to chase down a vacuum leak and just eliminate that as that would be the likely cause of something like this.
Here is a guide that will help find it:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
Tuesday, August 3rd, 2021 AT 8:44 AM