I just checked my tire pressure cold on my new 2014 Civic. It uses the nitrogen in the tires. We just had a change in temperature of about 15 degrees cooler in the past few days. The pressure sensor warning displayed. I checked the tires cold and they were all around 31 psi which on the door states PSI of 30. All that said and done -- Is it normal for these sensors to register a problem when the PSI in all 4 tires is good?? Now lets say the PSI changes about 1-2 PSI will it give this reading and is this normal for all correctly operating sensors?? All my cars before this did not have these sensors. Is this normal??