Will built in alarm system ever shut off by itself?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by pasadena_commut, Mar 29, 2021.

  1. pasadena_commut

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    If the factory alarm system is enabled, and then triggered, will it shut off automatically eventually, or will it just sound the horn for as long as it takes to discharge the 12V battery?

    In researching this I have found references to actions someone with the fob can take to turn it off, but nothing about it shutting off after some time period. Before wiring in a tilt sensor it would be good to know that if it triggers in an airport parking lot (for instance) it won't blare for the next 4 days and leave the car unusable afterwards. The factory alarm is enabled on my wife's Accord (apparently since it was built) and as far as we can tell that one never shuts itself off, or at least the time to do so is greater than 30 minutes. So there is precedent for this sort of ill behaved alarm system. If the Prius factory alarm doesn't time out, and there is no simple way to wire in a shutoff timer, it looks like some after market alarm would be a better option.
     
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  2. pasadena_commut

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    Documented on page 11 of the "Theft Deterrent" manual.

    Supposedly it shuts off by itself after 60 +/- 5 seconds, at which point it returns to the "armed" state.

    Unclear what happens if a door is opened in the "armed state" and stays open. After 60s it is supposed to go from "alarm sounding" back to "armed", but the same transition table says that "armed" goes to "alarm sounding" when a door "opens" (not "open"). The computer might define "opens" as the downward edge of the door switch voltage. If that was the case it would not see it "opens" on the second go round, because even though the sense line has been pulled low there would be no transition to that voltage. Alternatively, if all it looks at is the voltage (or current) on the sense wire I would guess the alarm would fire up again immediately.

    Guess I should disable the horns so it doesn't drive the neighbors crazy and try this out, to see what actually happens.
     
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