security system oddities

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by pasadena_commut, Oct 2, 2021.

  1. pasadena_commut

    pasadena_commut Active Member

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    Before I (finally) enabled the security system the active state values for "body" were examined and there were two security related oddities.

    The first is that it showed "glass break sensor detector" as ON even though I am pretty sure there is not one installed in this base model.

    The second is that the "hood courtesy switch" showed OFF when the hood was open AND when it was closed. The black plastic shield at the front of the engine compartment was removed, and that revealed two white tubes about an inch long coming sideways out of the latch towards the drivers side, to an electrical connector with a cable plugged in. That is probably the wiring for this switch. This thread mentions the same device:

    sensor or other device on hood latch | PriusChat

    Anyway, it does not seem to do anything. Now that the alarm system is enabled it was tested, I think, by locking the car with the window down, waiting >90 seconds, then reaching in and pulling the hood release. Nothing. Release the latch and lift the hood. Nothing. Verified that the alarm was indeed working by opening a door. Horn sounds. If that isn't a valid test of this device, what is?
     
    #1 pasadena_commut, Oct 2, 2021
    Last edited: Oct 2, 2021
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    The manual shows the hood latch switch should be open circuit when the latch is closed and have continuity when the latch is open. The two wires are a signal from the body ecu and a ground. So when the latch is closed the signal wire should have some kind of voltage present. When the latch is open it SHOULD pull the signal to 0V- that assumes that the switch works and all wiring is intact.
    Your function test merely confirmed what the scantool already showed- that the body ecu doesn't see a change in the hood switch signal. You need to do some testing to figure out WHY. You can use a multimeter to check voltages at the switch or check resistance across the switch, or just carefully jumper the two circuits together and see if Techstream shows the hood as "open".

    Posted via the PriusChat mobile app.
     
  3. pasadena_commut

    pasadena_commut Active Member

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    Couldn't find diddly squat about replacement hood courtesy switches for the Prius - no part number, no pictures. There are replacement latches, and most of them indicate that either they don't have the alarm part, or the picture does not show it.

    There is a video showing somebody pulling one off a latch and cleaning it on aToyota "Hilux Vigo", whatever that is. The dialog is in some language I don't speak, sounds like Tagalog, so not much point listening to it. But it does show how Toyota designed at least one of these.



    This ebay item gives the best view of the switch on a Prius that I have found:

    2004 2005 2006 2007 2008 2009 Toyota Prius Hood Latch Assembly | eBay

    It looks like the two white tubes may measure proximity to the metal hook shaped piece in the latch, which may move. The whole white piece seems to clip through the latch with a tab very near where the cable plugs in. It does not look anything like the part in the video. It does not look like anything moves in it, there is no lever to depress a button, as there are on most things like this. Unless I finally locate a place to buy a replacement, and assuming it is the switch which is bad, it would probably be easier to wire in one of these instead:

     
  4. pasadena_commut

    pasadena_commut Active Member

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    Yesterday that white doohicky was visually examined closely while the latch mechanism was open and closed with a screwdriver (which takes a lot of force). It would have been better to get some multimeter probes on it and the cable, but removing the vanity cover didn't provide enough space, and I wasn't feeling motivated enough to take the bumper off. Anyway, the release cable goes by just under the two tubes, but the rest of the latch motion is far away. Also that white plastic piece is not stably mounted, it is just attached by a clip through one hole in the latch metal, and it can move around quite a bit when pushed with a finger. In short, I don't think it is any kind of switch, but rather just a bit of plastic to terminate the cable which would go to that switch if one was present. The manual section on the hood courtesy switch shows a device similar to in that video. However, I could not see any mounting holes inside the latch which would have held such a switch. I think maybe Toyota sells two types of latches, one with a switch, and one without but with the white doohicky. Unfortunately I have not been able to find a part number for the first type.
     
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