The 2012 Fit has discrete TPMS sensors (unlike the 3rd generation that has a passive monitoring system using the ABS wheel speed sensors). If the low pressure warning light goes on, it should be rectified by filling the tires to the specified pressure (overfilling it a few pounds won't matter as the system is looking for low pressure, not overpressure) and then driving the vehicle should cause it to reset. I believe it has to go over 20 mph for the sensors to begin transmitting the signal.
If you know someone with a TPMS tool, have them check each sensor to be sure it's transmitting the correct data. We know all 4 sensors are transmitting because otherwise the TPMS light would be on, not the low pressure icon. However, it's a slim possibility that a sensor could be transmitting say 20 psi even though you have 33 psi in it. I've never seen this occur yet, but anything's possible.