I had an alarm from a motion detector go off erroneously. The 2gig system has been installed for approximately 2 years. Might the original batteries of the motion detector need replacing and would low batteries for motion detectors cause the faulty alarm? Also, do the motion detectors provide a warning when the batteries are low (similar to the thermostat battery notice I received)?
While records do not indicate the motion detector in question has a low battery, it is certainly possible for a borderline low battery to cause issues. Especially if the batteries involved are the original batteries, depending on use. When the batteries are low enough they will produce a low battery warning.
If you have a mulitmeter you will want to test the batteries to see how many volts they produce.
Some other issues to look at:
Placement and field of view, is the motion detector in question near any vents? The blowing air can activate them.
Small pets? They can often set off motion detectors, especially cats.