Care to weigh in on this locking/horn/flasher issue?

Discussion in 'Gen 3 Prius Technical Discussion' started by 134HP Bard Womyn Magnet, Oct 27, 2021.

  1. 134HP Bard Womyn Magnet

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    Edit: ignore the horn aspect of the post title, resolved by RTFM :cool:

    Hello. I have another thread regarding the hazard flashers not working on a new-to-me 2014 Prius 5 Hatchback. Now the hazards work via direct wire to with the hazards button, but they're now isolated from the rest of the system, so when I lock or unlock the car, they don't flash. I just get the lock/unlock beeping sound, which makes sense.

    Once I have some time, it would be nice to resolve this and get it all working again. When repairing, I saw at least one wire was cut going into the relay (photos in thread). I know repairing this would be the most obvious start, but access to the L55 turn signal/hazard relay is super tight and would require disassembly of the dash and/or replacing the wire harness. So I'm trying to gain insight into why wires were cut first. I have a feeling it was unfinished "troubleshooting" or - more likely - a quick "fix" by a mechanic that was never undone (see #2 below), but anyway, some questions:
    1. The previous owner had an aftermarket remote start that was installed then removed (he claimed it drained his battery, no idea if true). Would an aftermarket remote start even have any involvement with the wires into the hazard/turn signal relay?
    2. I saw the body ECU was replaced 6 months before I bought the car. Can anyone confirm it is the body ECU that is responsible for the blinking of hazard lights on lock/unlock? Seems like it should be, confirmation would be great, I lack a service manual for the moment.
    Thanks for any input.
     
    #1 134HP Bard Womyn Magnet, Oct 27, 2021
    Last edited: Oct 27, 2021
  2. rjparker

    rjparker Senior Member

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    It is a common fix for erratic and undesired flasher operation. Most likely an ecu fault on that line. Perhaps someone suspected the body ecu. Maybe its fixed and only needs the jumper as previously discussed. Or maybe its the skid ecu and they punted. 2D76A5AA-9FB8-4F1E-82BF-F61A198039D1.jpeg
     
  3. 134HP Bard Womyn Magnet

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    Thanks for the diagram. Yep, I was actually kinda psyched when I got the service records yesterday and saw the body ECU replaced recently. One less thing to do, I hope.

    On the other hand it was also a bit alarming...especially seeing what appeared to be a tow charge. I also saw an ABS sensor and wire replaced, which makes me wonder if you're right about the punt. Their notes:

    Performed computer diagnostics, no codes stored. Only code for R/R wheel speed sensor. After conducting multitude of circuit tests, removing interior and checking all powers and grounds. Performed circuit integrity testing and scoped Can bus waveforms. Tech found issue to be from main body ecu and signal from IDM, intermittent communication problem from body. Need to replace Body module and reprogram ECUs.
     
  4. ChapmanF

    ChapmanF Senior Member

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    There's a commonly-reported issue that has its origin in the brake ECU (not the body ECU). In a manner that's not completely pinned down yet, a perhaps-intermittent short develops between two adjacent pins of its connector.

    [​IMG]

    The only official solution is to replace the brake ECU—which is all one assembly with the master cylinder, booster, stroke simulator, and ABS actuator. An expensive part and also a pain in the butt to replace (not to mention the kind of a job that leaves you with an unsafe car if not skillfully done).

    That's the thermonuclear-flyswatter solution to what is probably a fairly simple problem. But it is the official solution, and if you've got that kind of money, and you want the fly dead, it will work.

    The previous owner probably just preferred to snip a wire.

    So far, the member who has made the most progress on getting to the bottom of it is @LeftyLucy. Maybe it would be worth finding some way to join forces?

    [​IMG]
     
  5. 134HP Bard Womyn Magnet

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    This is like a celebrity response for me because I read through that post like ten times when trying to figure out my hazards issue! And @LeftyLucy is in a different league, I don't think I'd add much to the team. I couldn't have diagnosed and "fixed" (hacked) the hazard issue without this board and pretty much just copied what was done. I don't wanna experiment with this and suddenly find myself without brakes.

    That is a maddening proximity on those pins. Very seductive theory. I guess SP1 could be next to something more mission critical than the HZRI pin. I'm trying to find a silver lining here. Sucks to have disco hazards synched (or inversely synched, according to another post) to your speed, but at least you can still drive the car...

    Gonna leave it alone for now...I still am tempted to restore the original state of that wiring assembly to see what happens if I ever have the car in a state where L55 and the connector are easy to reach and work on.

    I take it the installed/uninstalled remote starter can be removed from the equation?
     
    #5 134HP Bard Womyn Magnet, Oct 27, 2021
    Last edited: Oct 27, 2021
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