[werk_ag]

Werk,
Below is the code from the serial monitor of the CO2 sensor; every time it does a read it returns an error.
...

Hi Jim,

Sorry for the late reply.
Usually a read error is caused by problems with the serial connection to the sensor.
If you want you can try the attached MH-Z19 test software. It tries to read the MH-Z19 at each 8 seconds, and outputs data to the LCD and the Serial Monitor.
There is no need to do any configuration, it works with models A and B.