All lights on, no DTCs, no READY

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Mark222, Jan 6, 2025 at 10:43 AM.

  1. Mark222

    Mark222 Junior Member

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    Hi all, trying to figure out what is going on with a friends gen3 Prius. Would not start this morning, all the dash lights are on (at least I think this is all of them):
    upload_2025-1-6_10-36-39.png

    upload_2025-1-6_10-36-53.png

    It does not show READY and will not shift out of PARK.

    I connected techstream (v15 which is VERY old, predates the gen3). Ran the health check and it show no DTCs except an old ("history") B2325 which from what I read has to do with window motors and would not stop the car from running.

    upload_2025-1-6_10-39-20.png

    upload_2025-1-6_10-39-41.png

    Any ideas where to start with this?
     

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    #1 Mark222, Jan 6, 2025 at 10:43 AM
  2. Brian1954

    Brian1954 Senior Member

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    Well, it looks like you do not have the red triangle (master warning light). Version 15 of Techstream is not very old. It should work for all Gen 3's without any problem. It looks like it is not detecting all the trouble codes that the car has. You should have codes for the two TPMS sensors that are not working and many more codes based on the warning lights on the dash. Something very strange is happening.

    What cable are you using between the computer and the OBD2 connector on the car?

    When you ran the health check, did you notice any communication error messages?

    What year is the Prius, and how many miles on it?
     
    #2 Brian1954, Jan 6, 2025 at 10:39 PM
    Last edited: Jan 6, 2025 at 10:56 PM
  3. Mark222

    Mark222 Junior Member

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    Yeah I was very surprised that with all the warning lights there were no codes. I am using a cheap OBD2 to USB cable which I have used on many Prius cars with no problem. On this car it behaves normally, flashes green as data is transferred, no com errors reported by techstream. It read the car VIN number and a single the old (history) DTC so there does not seem to be any communication issues. The health check took a while as it walked through all the systems as expected, USB adapter flashing green, etc.

    Since it took all day for my post to be moderator-approved :( I did some more reading. This Prius model has a 'low aux battery' sensor and warning message which should appear if the 12v battery is low. That dashboard message never appeared, but I went ahead and checked the 12v battery levels at the jump point in the fuse box. With the car off it was reading ~10v, with the car ON and headlights ON, about 8.2v.

    I will pickup a new battery and install it today (in 30 degree weather, yea) and report back on results. I don't understand why the 'low aux battery' warning is not displaying, that is the whole point of it, right?
     
    #3 Mark222, Jan 7, 2025 at 9:36 AM
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  4. Brian1954

    Brian1954 Senior Member

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    Install the new 12v aux battery and see if the car starts. I assume that it will. Turn it off and connect the Techstream interface cable. Then, put the car in accessory mode (two pushes of the start button without foot on the brake) and run the Techstream health check.

    With the 12v battery as low as it was, the many ECU"s in the car were not able to initialize (boot up) and communicate with Techstream. I am guessing that the new 12v battery will make the car work properly again.
     
    #4 Brian1954, Jan 7, 2025 at 1:29 PM
  5. Mark222

    Mark222 Junior Member

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    Yup, after battery replaced it turned on, took a minute to sort out and turn off all the dash lights. Engine started and everything running normally. Good idea to re-scan all the ECUs now just to see if anything else is going on..

    Thanks!
     
    #5 Mark222, Jan 7, 2025 at 5:14 PM
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  6. ASRDogman

    ASRDogman Senior Member

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    The 12v is the first thing that should be checked because a weak one causes all kinds
    of issue like this one.
    You should charge the new battery for 6 hours or so at 5 amps or less to make sure it's
    fully charge and you won't have any other issues.
     
    #6 ASRDogman, Jan 7, 2025 at 6:41 PM
  7. BiomedO1

    BiomedO1 Senior Member

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    The battery icon was lit on your dash board. Probably not enough juice to fire your body control ECU to display the low battery message. Battery and fuses are the first things to check on these cars when they're behaving badly. I'm surprised you were able to maintain 8vdc with the head lights ON. That's how I troubleshoot a battery issue, without going after my meter. Go back to the garage n grab the jump box and meter to verify, then start the car.
     
    #7 BiomedO1, Jan 8, 2025 at 12:25 PM
    Last edited: Jan 8, 2025 at 12:31 PM
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