As said just measure, when duff they tend to go mega rich/high signal reading, or stop reading altogether.
They are just a simple wheatstone bridge affair, with a voltage scan of 250mV(0.25V) to 4750 mV(4.75V).
The scale is 15.46mV per Kilopascal, if you want to work out exactly.
The 2 bar is 22.61mV per kilopascal.
Each has 17 different steps/outputs.
tabetha