I did a search for "TPMS" in this forum and came up with many previous threads. I scanned about 3 pages worth and didn't see any that matched my symptoms, so here goes ...
2017 IS-Fsport with 87k miles. All original TPMS sensors. No recent work done.
When I start the car, the TPMS warning light comes on and turns off with the rest of warning lights. TPMS display shows "---" for all 4 tires.
I press the reset button that's below the steering wheel until the warning light blinks 3 times. The tire pressures still show "---" even after driving around for a while (I've seen 20 mins. mentioned as how long the car may need to be driven before the tire pressures are displayed) in my case the display remains "---".
If I shut the car off then start it again after the reset, the tire pressure for all 4 tires usually display and remain displayed for as long as I have the car on. If the car has been running for a short period (20 mins or less) and is the shut off, then re-started the pressure readings all go back to "---".
If I drive for an hour or longer after getting the tire pressure readings back and then shutting the car off, the readings will come back if the car is re-started after 10 or 15 minutes. If left overnight, the readings return to "---".
I've even tired pressing the reset 3 or 4 times while the car is running to get the pressure readings to appear without the need to shut the car off/on, this works sometimes, but the "---" return after an off/on sequence.
Can a "weak" TPMS sensor in one or more tires cause this?

Any words of wisdom would be greatly appreciated!

 

Did you ever scan OBD2 to read TPMS error code? I have same issue and poping up TPMS error code "C2122, C2124, C2177 and Transmitter ID Not Received (Main)" message. But I know my TPMS not working because sensors batteries died. I would suggest go to a tire shop or walmart auto center and let them check the sensors signals. I don't recommend to go a Lexus dealership because they do too much expensive even for quick diagnose.

 

Your sensor batteries are at least 7 years old. As said above, have a tire shop read the sensors, they usually report battery strength too. You probably need new sensors.

 

I went to a local tire shop (I needed 2 new front tires). Started the car, the display was all "---". Stopped for coffee, re-started the car and now all the pressures are reading (I did not press reset).
Tire shop checked the output of the sensors, all were OK and the display was reading properly. They said that if this is bothering me (it is), that I should have the dealer look at it.
I get in the car, start it up and the "---" are back!

 

For me, it takes a few minutes for the "--" to go away and the numbers to return. Even if I switch the car to accessory mode, after about 60 seconds or so, I can see pressures.

 

Mine does this sometimes which is fine and not part of what I consider to be the problem. I've had instances where no tire pressures were displayed for trips of an hour or more.

 

Same issue for me . Keep me posted on fix.

 

Well, our long national nightmare is over.
The idiot light finally came on and I got a message on the display that there was something wrong with the TPMS system.
They were able to scan out code C2122. Replaced one of the tire sensors and all is now well.
$100 for the new sensor and tire re-mount.
The next time this happens, I'm gonna change the remaining 3 original sensors.

 

Thanks for posting the result. My car is almost 7 years old. I don’t have your problem but as a preventative measure, I plan on changing all TPMs sensor the next time I buy new tires, which I suspect will happen in 2026.