1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Prius Immobilizer

Discussion in 'Gen 3 Prius Audio and Electronics' started by aspacardin, Apr 21, 2015.

  1. aspacardin

    aspacardin New Member

    Joined:
    Apr 21, 2015
    1
    0
    0
    Location:
    Greece
    Vehicle:
    2012 Prius Plug-in
    Model:
    N/A
    I need to install a gps monitoring system on a prius (and some other pure electric cars) used for rentals. We also need to be able to do remote immobilizing of the car. On our gas powered cars, we normally install the immobilizer on the engine starter, so there are no safety concerns while there's someone driving the car. Where could we install the immobilizer on the prius, so that if something goes wrong with our gps device, the car still works if there is someone driving it, but it can not be restarted once it stops?
     
    #1 aspacardin, Apr 21, 2015
  2. jdenenberg

    jdenenberg EE Professor

    Joined:
    Nov 21, 2005
    3,852
    1,853
    1
    Location:
    Trumbull, CT
    Vehicle:
    2020 Prius
    Model:
    LE AWD-e
    If you disable the brake switch, a Prius cannot be put into "Ready" mode after it is turned off.

    JeffD
     
    #2 jdenenberg, Apr 21, 2015
  3. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,332
    10,175
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Is that the same switch that triggers the brake lights? That sounds like a road hazard. This would be safe only if the ignition interlock uses a separate brake switch.
     
    #3 fuzzy1, Apr 21, 2015
  4. qdllc

    qdllc Senior Member

    Joined:
    Aug 25, 2013
    1,370
    399
    0
    Vehicle:
    2013 Prius
    Model:
    Two
    If the immobilizer has a fail-proof "logic" circuit, you could use the brake switch. Meaning, if you activate it, it won't engage until the power to the car cuts off, then depressing the brake won't work. No danger of cutting off someone's brakes while operating the car.

    Have you chatted with Toyota on this? I'm sure their anti-theft features may already do this and only need to interface with the immobilizer device.
     
    #4 qdllc, Apr 22, 2015
  5. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,332
    10,175
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    It isn't the brake function I'm concerned about, the switch won't disable that.

    But the brake lights are a required safety function to warn the driver behind that the brakes are being applied. The switch that operates those warning lights cannot legally be disabled. Does the ignition interlock use this same switch, or a separate switch?
     
    #5 fuzzy1, Apr 22, 2015
  6. qdllc

    qdllc Senior Member

    Joined:
    Aug 25, 2013
    1,370
    399
    0
    Vehicle:
    2013 Prius
    Model:
    Two
    I'd have to see a wiring diagram. If the brake pedal energizes two circuits (one for lights, one to tell the computer the brake is applied), you'd only need to disable one of them. If the computer uses the brake light wire to determine if the brakes are applied, yeah, that'd be an issue.
     
    #6 qdllc, Apr 23, 2015
  7. jdenenberg

    jdenenberg EE Professor

    Joined:
    Nov 21, 2005
    3,852
    1,853
    1
    Location:
    Trumbull, CT
    Vehicle:
    2020 Prius
    Model:
    LE AWD-e
    I can send the OP the wiring diagram for a Gen2 if it helps. It is large (6.5 Mbytes) so he would have to PM me his email address. I do not have Gen3 documentation.

    JeffD
     
    #7 jdenenberg, Apr 23, 2015
  8. macman408

    macman408 Electron Guidance Counselor

    Joined:
    Mar 21, 2010
    1,179
    366
    1
    Location:
    California
    Vehicle:
    2010 Prius
    Model:
    V
    It's possible. The manual I have seems to show that the stop light switch is a DPST switch with one normally-open and one normally-closed. The normally-open side looks to be connected to the battery more-or-less-directly, while the normally-closed side looks like it might only be connected to the battery when the ignition is on. It's hard to tell though, because the information is split between multiple diagrams (and which side is normally-open changes between them).

    Looking at it more, it seems like the normally-open side is used both for the Power Management Control ECU (which I assume is responsible for starting the car when you press the power button) and the stop lights, while the other side is probably to detect a failure in the stop light switch (which would cancel cruise control, illuminate the CEL, and who knows what else).

    So the way to do it would probably be to insert it as close to the power management control ECU as possible; the other ECUs and the brake lights will hopefully get the correct signal, which looks like it gets forked off (at least to the Driving Support ECU, Stop Light Control Relay, and Skid Control ECU/Brake Booster with Master Cylinder). While driving, there'd probably be some warning lights as it detected the malfunction, but it'd probably still drive safely. And presumably, it wouldn't start again.

    Of course, if you dare to try that mod, be sure to test it out while moving very slowly in a very empty parking lot. :) It's not something I'd try!
     
    #8 macman408, May 2, 2015
(You must log in or sign up to post here.)