First try the following:
1) Connect the sensor to a Vernier interface and the default readings in kPa are NOT around 101 kPa
2) Connect the 20 mL syringe from the Accessories Kit to the sensor, move the plunger inward and the pressure readings do NOT increase.
If both of these tests fail, there may be a few additional things you can do to restore the sensor:
A) *Check calibration values**
Sometimes students will 'zero' the sensor causing readings to be quite off. To double check that this is not the case, restore the factory calibration. To do this: enter the calibration screen in your data-collection software and click on the "Storage" tab. Click on the "Restore Sensor Factory Default" button. Repeat steps 1 and 2 above. If the problem is not fixed, continue to B.
B) *Check for corrosion**
Sometimes the BTA cable of the GPS can get corroded and cause the readings to be off or even for the sensor to not identify. You can clean the end of the cable yourself by brushing the corrosion off with a stiff wire brush. To prevent this from happening in the future, make sure you are storing your sensors in a cool, dry place that is well-ventilated. Do NOT store them in a chemical storage cabinet or near volatile chemicals.