I think you have to degas to remove the sensor and test properly.
I have no idea what access is like without dismantling the dash, but if you can get to the connector, you might be able to test the resistance of the the sensor, to see if it's sensible and not shorted, etc., and give the loom a check for short too.
You might find more info in the manual
http://hondafitjazz.com/manual3/