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Another weird sensor thing ☹️

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Chris Wolfgram, Jul 4, 2024.

  1. Chris Wolfgram

    Chris Wolfgram Active Member

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    2019 Prius
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    LE
    Okay, here we go again. So yesterday it was cooking hot here in Sacramento CA.... About 110F. and my 22' XLE was parked facing straight into the sun.
    So I hop in it, start to drive and I get a pop up... Which (I think it said) "Front collision camera not available"....
    Huh ? Okay. So I get on the freeway, go to hit cruise control, and it wouldn't let me use it, but kept popping up with "Front collision camera not available" ?
    So while driving, I'm looking at all of my dash lights, and the "check engine" indicator was NOT on, so that's good. But oddly, I see a tire pressure indicator light is ? Also, I had the yellow triangle warning light about the gear indicator.
    So when I got home, I checked all my tire pressure...I think one might have a slow leak, maybe around the bead, but it was only 32 lbs (on a very hot road) but the other 3 were at 42 lbs. I think my mechanic puts 36 in them, but it was probably 80F degrees when I saw him last, so I'm pretty sure that was why they were at 42. None the less, I lowered the 3 tires to 35 lbs.
    Hopped back in the car, fired it up, and now the warning ⚠️ symbol has gone away, and my cruise control works again.
    Only thing is, the little indicator that shows the cross section of a tire with the exclamation point is still on ?

    Will that clear itself after a certain number of restarts ?
    Is it possible that one of my tires individual sensors has gone out ?
    My mechanic said we can throw it on his scanner to see which tire is causing that... But that's about an 80 minute round trip, so unless I was going that way anyway.... Or during my next oil change....
    Granted, if my car lost cruise control again, id probably have to take a drive...
    Any of you have any experiences like this ?
    Any guess as to what's really going on ???
     
  2. ChapmanF

    ChapmanF Senior Member

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  3. FuelMiser

    FuelMiser Senior Member

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    The proper way to handle TPMS warning is: 1) Check ALL tire pressures because Prius does not tell which tire(s) is / are low (you did this), 2) Set all tires to recommended (or preferred) pressure--seems you reduced three tires to 35 and left one at 32, 3) Reset the TPMS using the Vehicle Settings page. You did not do this. The TPMS light will not go out until you RESET the system in the Vehicle Settings menu.
     
    AzWxGuy likes this.
  4. BiomedO1

    BiomedO1 Senior Member

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    The reason your cruise control wasn't working is that part of your safety system was "blind", literally. Once the camera cooled down, it became functional again. Therefore your cruise control started working again.
    Tire pressures, Your suppose to check them in the morning. Not mid afternoon after running on the hot tar mat. If you now check them, as prescribed by your operations manual, you'll find that they are low. The air in hot tires expand, throwing off your measurements. You need to get that leaky tire fixed, before you blow it out - you don't have a spare so you might get stranded on the side of the road without cell service.

    Hope this helps....
     
    #4 BiomedO1, Jul 5, 2024
    Last edited: Jul 5, 2024
  5. ChapmanF

    ChapmanF Senior Member

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    Although this has changed from a pushbutton in gen 3 to "Vehicle Settings" in gen 4, the passage in the 2019 Prius owners' manual does not suggest that its purpose has changed:

    [​IMG]

    You would necessarily do this if you have changed your mind about what your normal tire pressures should be. Then you make sure they are aired up to your new preferred pressure, and use this procedure to have that new current pressure remembered as the benchmark.

    If the system was already set for the right pressures, but the light came on to warn you of something, it still remembers what the benchmark pressures were from before. There is no need to set them again, if you have not changed your mind about what they should be.

    If the warning was about a tire pressure too low, the warning will go away after a bit of driving, once the pressure has been corrected.

    Sometimes the light is on to warn of something else besides a low tire pressure. For those cases, getting the trouble code can help figure out what the warning is really about.
     

    Attached Files:

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  6. Doug McC

    Doug McC Senior Member

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    I can verify the part regarding the automatic reset of the tire monitor: recently had a leak in one tire, brought it back up to normal pressure and the light went out.
     
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  7. Doug McC

    Doug McC Senior Member

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    Check your owners manual. (Page 289 in mine). It spells out quite specifically why your Dynamic Cruise Control acted that way. Basically, it is normal.