The computer must be connected to a myriad of sensors, from door locks, window position and all the other system parameters. Depending on how it's programmed, it seems to ignore some functions at times. Some of the time, the auto-unlock function just seems to refuse to work. It doesn't seem to matter how I place the key fob, the door will not unlock. Is this due to the programming or perhaps a bad RFID sensor? I have raised this issue several times with the dealer, but they say they can't reproduce the error. Is there some way to test this?
There are a multitude of computers, talking with each other over networks. Around two dozen of them in gen 3—I hesitate to guess how many in gen 5. For the functions you're concerned about, the Body ECU, smart key ECU, driver door master switch ECU, or whatever their equivalents are called in gen 5, would probably be the ones most involved. The details would be in the docs: Toyota Service Information and Where To Find It | PriusChat
It could be the way software was written. Certain aspects of the operation are critical, and likely receive priority when there aren't enough clock cycles to do everything.
Fewer computers in the gen5 compared to the gen3. The gen3 was probably the peak of discrete computers. After that, the computers got powerful enough to handle multiple systems, so fewer were needed. On top of that, you have the push towards more complicated canbus/multiplex networks which, ironically, need fewer computers and wires. The positives are that there is much less wiring and computers in current cars. The negative is that the remaining computers are that much more expensive to replace. As for Paul's question, he doesn't give enough info to really figure out what's going on. What auto-unlock function is he talking about? My suspicion is user error, but there's no way to know with the limited info. The reason I think user error is because he mentions the positioning of the keyfob. The only time the position of the fob matters is when the battery in it is dead and you need to start the car. Then you have to place the fob on the power button so the car can read the fob's weak signal. Other than that, the position of the fob doesn't really matter. If you want to unlock the door the standard way, the fob just needs to be within a meter or two of the car. The trigger to unlock is when the car detects the water inside your hand as you put your hand inside the door handle. To actually answer the question, Paul would need to describe exactly the behavior he expects from the car, exactly what he's doing, and exactly what the car is doing/not doing in response. The more detail the better.
