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Discussion Starter · #1 ·
Before I posted this inquiry, I had a look at various posts with similar problems. None had all of them together. (Perhaps I shouldn't say this, but our 2019 Pacifica has been pretty good so far.)

We got a little over an inch of rain here last night, which is really unusual. Relative humidity is 50% and the temperature was about 83F when the event took place. Daytime temperatures have been ranging from 115F to 99F, dropping to 90 at night. Relative humidity has been in the 30% range.

My wife had to make a 25 mile round trip this morning. A few minutes after she left, she called to tell me that the tire pressure warning light was on, saying that the RF tire was at 30 PSI, but the other 3 were about 36. I told her to finish her errand and I would check things out when she got home. (These are the horrid OEM Yokohama Avid S34 tires that have a sidewall max pressure of 45 PSI. I keep them at 41 PSI, but they ooze air.)

Her errands were uneventful, so far as the car was involved. When she returned, I checked the hot tire pressure on all four using a good dial pressure gauge. All four of the tires registered 40 PSI.

So she got into the car to find out if the four-tire on-board pressure indication was now reflected by the sensors and display. Car would not start. The only display she got was the green light next to the "start" button that indicated the fob was in the car. I got in and had the same result. I gave the "start" button several really sharp jabs, and the car started. (Yes, both of us had foot-on-brake.) Both of us then stopped and restarted the engine several times with no difficulty.

Tire pressure display still showed 36 PSI and a lower number on the RF, but not low enough to trigger the warning. Yet my gauge measured 40 PSI in all 4. We used to get haunted minivan syndrome problems with our 2007 T and C when the battery began to go south. Similarly, we have had battery problems with this one. But in this matter, do we take the car to the dealer (who has been pretty good), a for-real battery shop, or to Discount tire for tire sender calibration? Or all three?

Salient information:
2019 Pacifica L, under 10,500 miles
Main battery status: On its third main battery; first an OEM, then a dealer installed NAPA, now a MoPar AGM.
Aux battery status: On its second or third battery.
Has collision avoidance system, lane assist and multiple cameras. No high-end doo-dads such as DVD players and seatback and right side USB ports.
Has the common dashboard click after turning off the car.
The radio will reboot spontaneously. Will turn back on if left turned off for a while. Can't tie this to battery condition.
 

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Key fob and tpm sensors could have failing batteries . The sensors are battery driven and you don’t know the date to which they were installed , so fob and sensors could be on the verge of failing .
 

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The key fob was my first thought after mentioning the issue with the multiple Start presses.
A test for this could include two procedures. One is seeing how many successful starts there are when holding the fob to the start button. Next I would try starting the engine with the key fob in the passenger seat, then the second row, and finally the third row. See what the success rate is? Battery strength?
As for the tires it probably is a failing sensor. The weather may have accelerated an issue? Is 40psi suggested as the pressure listed on the driver door?
 

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Discussion Starter · #4 ·
Key fob and tpm sensors could have failing batteries . The sensors are battery driven and you don’t know the date to which they were installed , so fob and sensors could be on the verge of failing .
The key fob was my first thought after mentioning the issue with the multiple Start presses.
A test for this could include two procedures. One is seeing how many successful starts there are when holding the fob to the start button. Next I would try starting the engine with the key fob in the passenger seat, then the second row, and finally the third row. See what the success rate is? Battery strength?
As for the tires it probably is a failing sensor. The weather may have accelerated an issue? Is 40psi suggested as the pressure listed on the driver door?
Thank you Canada Hybrid Guy and Jerith. I will check all of these things. They all make sense. The fob that was in use at the time was the fob that my wife carries, so it gets the most use.

Weather here during the summer is usually relative humidity under 10% (usually 5% to 7%) with temperatures of 110F to 118F (46C to 49C by my mental calculation.) That sort of weather ruins batteries, but raising the humidity to 40% without lowering the temperature makes weird things happen. I don't recall the driver door recommended pressure, but it only applies here on New Years Day when it is circa 70F (23C) outside. So I always inflate to the sidewall max temperature during "regular" weather. Tires are less likely to fly apart due to underinflation that way. Trying to get it right with the ghastly OEM Yokohama Avid S34 tires has been difficult.
 
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