TPMS Receiver or Computer?

Discussion in 'Gen 2 Prius Technical Discussion' started by Pukawai, Mar 16, 2023.

  1. Pukawai

    Pukawai New Member

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    I finally got around to doing something about that annoying TPMS light. I got one of those VCI cables with the hacked techstream software and finally got it working. The TPMS section showed that all but one of the sensors was dead - not surprising since this a 2007 vehicle. I replace all the sensors and programmed in the new Sensor IDs. Techstream then showed air pressures for three of the sensors but not for what the software calls "ID2". Thought maybe one of the replacement sensors was bad and replaced it with the original sensor that was still working, but it still didn't show a air pressure - indeed, even if I just shuffled the sensor IDs around, the ID2 channel was still always dead so the problem must be with either the receiver or the computer module.
    Now, the question is: does the receiver module contain 5 separate receivers each of which is dedicated to one sensor, or is there only one receiver that the computer module polls to get pressure data for each sensor in series?
     
  2. PriusCamper

    PriusCamper Senior Member

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    Interesting question... I currently have a TPMS light that goes on only when I get up to freeways speeds for longer than 20 minutes and then goes away after a couple days of driving around town. I also am curious as to how the TPMS processing works and if it measures all four sensors in a dedicated way, or just polls them periodically. I bet @Elektroingenieur could explain this...

    I was thinking I simply have one failing TPMS sensor, but maybe the way the system works it's more than that?
     
  3. Elektroingenieur

    Elektroingenieur Senior Member

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    As Toyota explains in the Repair Manual (more info), there is only one receiver:

    A tire pressure warning valve and transmitter is equipped with a tire pressure sensor and is installed in each tire wheel assembly. The sensor measures the tire pressure. The measured value and transmitter ID are transmitted to the tire pressure warning antenna and receiver on the body as radio waves, and then sent to the tire pressure warning ECU from the tire pressure warning antenna and receiver. If the transmitter ID has already been registered, the ECU compares the measured air pressure value with the standard value. When the value is less than the standard value registered in the tire pressure warning ECU, the warning light on the combination meter turns on.

    The transmitters don’t operate continuously. The exact conditions aren’t described, but the test report (PDF) submitted for FCC authorization describes a ”rotating mode,” with transmissions every 64 seconds, and a “stationary mode,” with transmissions every 320 seconds, among others.
    Without information Toyota hasn’t published about how the system works, it’s difficult to say for sure what might be happening, but it could be that the heating from sustained freeway driving causes the pressure to increase enough, relative to the standard value—which might have been registered when the tires were cold, underinflated, or both—that the system warns you of overinflation. When the TPMS warning light is on, have you checked the reported tire pressures or for stored DTCs?
     
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    What sensors did you use? Have you driven the car for a few miles?- sometimes makes a difference on some cars.

    The Gen2 uses a single receiver. Can't say that I have ever seen a single "dead channel" on this type of system. (my experience has most ecu faults preventing ID programming from going through)

    Posted via the PriusChat mobile app.
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    These are the sensors I used. Worked fine.
    A7AFB804-98E5-44B1-B147-5650724BE745.jpeg

    5C3DF9FA-CA0B-4C3C-848C-5D34DA218CF3.jpeg
     
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  6. PriusCamper

    PriusCamper Senior Member

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    Yes, I forgot to mention these are brand new tires that I decided to take a chance on not replacing the TPMS sensors on when they were intalled and TPMS came on soon as that was done after first 20 minutes of freeway driving. On the bright side they were 2012 wheels with original TPMS sensors and have had no issue around town for 4 months & 4K miles. Only when I travel long distances.
     
  7. Tombukt2

    Tombukt2 Senior Member

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    And pumping up the tires to 48 lb up front and 43 or so in the rear seems like that would be getting up into the 50-some odd pounds heated or not cold. I used the Pacific brand sensors that Toyota sent with the car they make the center caps for your wheels It's printed on the back of the center caps It's also printed with a green logo directly on the TPMS sensor in the wheel ours are green they make some red ones I don't know the difference if it's frequency or what I bought the same green. I'm not whipped out the tec stream to attempt to register them I was going to take it by my friend's tire store just haven't got around to it. But what I have noticed is that with the new sensors installed in the wheels and mounted to the car the TPMS sensor light now flash is about eight times or two times per wheel It seems to me it's sensing that the sensors are in fact there and are somewhat working but are not registered when the ECU determines this it puts the TPMS light from flashing to solid. Now if while driving with the TPMS light solid. If a tire goes down the TPMS light will start to flash kind of like it would if the light was off so something seems to be happening. I'll try and get by this week and have my buddy run as wand around the car and put the light off and then I guess I'll be able to set my tire pressure with the button and all of that but I thought it was interesting that the sensors seem to be being sensed and somewhat working even with the TPMS light on.
     
  8. rjparker

    rjparker Tu Humilde Sirviente

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    With Techstream you can see realtime tire pressure and temp but not location. The seven digit "Registered ID Code" has to be identical to the ID code on the sensor. When changing sensors the vehicle stored IDs have to be changed.

    0DD58C96-B864-44EC-B12C-22FC71EA4AC0.jpeg

    In this case ID2 was not reporting properly. If you have an Autel tpms scanner, you can individual rf scan each tire to determine where each ID is currently located. Without the $150-$250 Autel, you either change them all or you reduce the pressure in each tire one at a time while watching Techstream. In my case ID2 was on the rear passenger tire.

    To program new sensors with Techstream, you go to the Utility item and follow directions. However the new sensor won't be read by the vehicle until it is installed and is driven above 20 mph. At that point the TPMS light will clear without needing an under dash reset.

    --------------------------------------------

    Finally, for those of you with a set of winter tires and wheels, some sensors such as the "Autel TPMS Sensor MX-Sensor" can be programmed with the ID codes from your summer wheels. As a result, no tpms registration is needed when swapping sets. The Autel MX sensors do require an Autel scanner although a $54 "Autel MaxiTPMS PAD" version is available for Windows PC based operation. This unit does not rf scan sensors on the car and only programs their MX sensors. upload_2023-3-17_11-38-39.jpeg

    https://www.ebay.com/itm/364074183648
    The $28 option is just one sensor.
     
    #8 rjparker, Mar 17, 2023
    Last edited: Mar 17, 2023
  9. Mendel Leisk

    Mendel Leisk Patron saint of newly poured sidewalks

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    Have you considered side-stepping the issue, ie: just fugedaboutit.

    When I got snow tires on separate rims for our 2010, over 12 years back now, the dealership mechanic asked if I wanted TPMS sensors, while shaking his head...

    I didn't need convincing, but it was nice to see I wasn't alone in my sentiment.

    They're great, can save your bacon, but Toyota's iteration sucks. On the plus side, if you need a hobby, getting Toyota's system up and running will keep you busy.
     
  10. Pukawai

    Pukawai New Member

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    Thanks for the replies!
    Electroingenieur - I'm impressed that you would actually have a link to the FCC report, as much as I am puzzled that a German company would be producing that report. The rotating mode would indicate that there is probably only one receiver circuit. It could still have 5 circuits but that wouldn't make much sense on a cost basis.
    RJParker - That's exactly what my screen looked like (except for the actual codes of course). But, if I shuffle the codes around so that a different sensor is "ID2" then it still shows N/A for ID2, so clearly the sensors themselves are all working. No, I don't have a $200 Autel, but I do have a $100 BeadBuster that I use to change tires on my motorcycle, and it works on the Prius tires too. Not too difficult, and it gets faster the more times you do it.
    Mendel Liesk - Yes, that is an option, but I already have one fugedaboutit sticker (aka a piece of black friction tape) on my dash covering the airbag light. The TPMS system IS of some minor use, and engineers are anal creatures that would prefer to fix it if the cost isn't too high...
     
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  11. rjparker

    rjparker Tu Humilde Sirviente

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    For $43 plus tax I would change them all. New IDs for each. Almost has to be a sensor but I suppose it could be a position on the car with weak rf due to old batteries and the body.

    There is just one antenna in the right rear. 0956AEE4-BBCE-4AD8-BE5B-8CA71AAAF684.jpeg

    Short of changing them all, I would do the reduced pressure test on each tire to id the physical sensor that is not reporting. Then move that tire to the opposite end or closer to the antenna.

    My experience when tests don't make sense and I am familiar with the logic and wiring; generally I have created a false negative on one of the steps. This leads to assumptions that are not correct.
     
    #11 rjparker, Mar 19, 2023
    Last edited: Mar 19, 2023
  12. Pukawai

    Pukawai New Member

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    Just wanted to update this. I got a TPMS receiver off Fleabay. I checked the Toyota fiche to make sure I was getting the right part number, but it lied. That part was brown with a 12 pin connector, but when I pulled off all the snap-together plastic crap to get at the part in the car, I found a somewhat smaller black part with a 5 pin connector. Then found one of those on Fleabay and installed it. I was actually surprised to find that the problem was fixed, I thought it was much more likely to be the TPMS computer - but at $6 the receiver was much cheaper to try first.
     
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