Carman only reads about 8 sensor. pyOBD reads several of them, depending on your car. On my smart, most of the sensor page is enabled and it reads all of them. I'm pretty sure pyOBD auto-detects what sensors it can get from your car, then shows them and updates them. If you're not seeing many (25+) active on your car, it's probably because your car doesn't support reading those in the same place the script is looking for them.

Volvo are great cars, but they're known for tweaking and customizing everything... including OBDII codes. smart does that too, but still accepts most of the older commands as well. The down-side for me is that lots of the "warning" codes show up as errors in pyOBD, and have no description, since they're manufacturer custom. I have an excel sheet somewhere with those though, and will add them (& upload them?) onceI find that again. It's on one of those thumbdrives... in that box over there... I think.