Ericahatch

Please help as I am at wits end. I have a 2010 RX 450h and the factory alarm randomly started going off at all hours about 5 months ago. The battery is brand new so it's not that. The alarm goes off at random hours in the middle of the night mainly and sometimes during the day. It doesn't go off every night; it is totally random and can go a day or two or three and then go off two nights in a row or multiple times in the same night. It stays on for about 30 seconds and then shuts off. I took it to the lexus dealership and they kept it for 5 days. They looked at everything and didn't see anything off. They even tried to gaslight me, telling me that they couldn't recreate the issue so it must not be a big deal (*they must not have stayed the night in the dealership with it!). I told them to disable the alarm completely and they said that this was impossible. I told them to disable the horn, and they told me that this was illegal. Their recommendation was to turn off the auto-arm and just leave the car doors unlocked all of the time so the alarm wouldn't set. (Yes, this was the solution). BUT, the setting that they put on it to not auto-arm doesn't do anything either. The doors don't auto-lock but the alarm still sets after all and then still randomly goes off. My entire neighborhood is ready to kill me, and the only solution I have now is to sell the car and make it someone else's nightmare.

I really thought I'd be a lexus owner for life but this is ruining my perspectives completely. Please HELP!

salimshah

There is something amiss.

Antitheft siren and horn are different items. [although they both produce sound].

With as assistant sound the horn to figure out which is the horn. Then disconnect the siren. Dealership is right to tell you that they can not disconnect the horn as it is deemed necessary for safety.

My #1 suspect is the hood closed/open sensor. For 450H, see if you get hood open message randomly.
#2 is the panic button on the key fob. Check and clean all key fobs as lint can get in them. Put the keys in faraday box to sequester them.

Salim

Clutchless

I think auto correct turned the phrase Faraday box or Cage into Fairy box.

For those unfamiliar with them:
​​​​​​A Faraday cage or Faraday shield is an enclosure used to block some electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials.

​​​​​​Do Faraday boxes prevent car theft?
Faraday bags, in essence, help to reduce the risk of your car being stolen. Most modern cars have many features that increase convenience and help to make life a little easier and one of those features is keyless entry.

Amazon sells them.

Ericahatch

I tried the suggestion but the alarm is still going off randomly, and even when we were out of town with the key FOBs with us. So it must be related to the car. The hood light has never been on.

I appreciate any other suggestions!