Chrysler Repair Questions? Ask a Mechanic for Answers ASAP
it the tire pressure sensor waning is flashing that means one of the sensors is either wrong or has failed NOT low air in the tires, the system will also set a fault stating which sensor(s) has failed, to get it you will need a TPM (tire pressure monitor) code reader tool, any shop that does tires should have one (snap on is the one that is most common) I would hope firestone (although they and most other chain shops are NOT known for quality just quantity) would have pulled the codes set and performed the necessary testing.
other problems can be with the receivers as well but you need the fault that is set, to know where to go, with a 12 year old car I would expect to need sensors as the batteries are designed to last 5 to10 years, and would not be surprised to see faults for low sensor batteries, in all cases with failing sensors or sensor batteries you need to replace the failed sensor.
IF the light stays on solid and constantly shows a low tire(s) verify the tire pressure is ABOVE the spec on the door at my dealer we set all pressures to 3 to 4 psi ABOVE the spec on the door usually 35 psi this eliminates the light from coming on when it gets cold, (as the temp drops so does the tire pressure, remember your basic science class in school) if the tire pressure checked with s GOOD digital gauge is low then there is a leak if nothing is in the tire then the rim is leaking USUALLY at the bead if you are in the snow belt the salt that is spread on the roads migrates between the tire and bead and corrodes the bead, the fix is clean the bead and use bead sealer on the tire
also IF the tire sensors have been replaced it is possible the WRONG ones were installed pacifica had 2 different sensors BOTH will train BUT will not read one was for premium systems and the other was for base (light ONLY) systems they are NOT interchangeable
following up to see if you need further assistance or were able to resolve your problem