2005 RX300 alarm going off

[LeoSteve]

Hi all 👋 I recently bought a 2005 RX300, and I've got a problem where the alarm goes off when opening the door after unlocking it.

I've owned the car for two weeks, and this has only started happening in the last three or four days. I've tried both unlocking with the key and fob, and it happens with both.

When the alarm is sounding, pressing the unlock button again stops it.

Any ideas on what it could be? I'm hoping something as simple as a low Battery in the fob.

 

Thanks.

[scudney]

Try changing the Battery in the fob and see what happens as a starting point 

[GMB]

I got a message on the dash " Battery low in key fob" then the yellow triangle was staying on for a few seconds with no other alert. Changed the Battery - job done no more yellow triangle. CR 2032 £1.50

[LeoSteve]

Thanks for the replies. With further investigation it seems like if the car locks itself, opening it with the key sets off the alarm when I open the door. If the car locks automatically do I then have to use the fob to open it? Or should it work with either?

[ColinBarber]

How is the car locking itself? That shouldn't happen unless you just mean you are unlocking with the remote and not touching a door for 30 seconds at which point it will relock itself (it's assuming you accidentally pressed the unlock button).

 

If the alarm is armed (by locking with the remote) then if you unlock with the physical key and open the door, the alarm will go off. The alarm isn't armed/disarmed with the key.

 

If you unlock with the remote, the alarm shouldn't go off (assuming a third party alarm hasn't been installed).

[LeoSteve]

That's right, sometimes I'll get out the car and I'll be pottering about with my bags, and it'll lock itself. e.g. at the petrol station this morning it locked itself while I was at the pump, I unlocked manually with the key, and the alarm went off.

The only reason I unlock with the key is habit. I upgraded from a Corolla, which had the exact same key, and the buttons stopped working 😅 

So it seems like it's my error. If I let the car lock itself, I need to unlock with the remote 👌Thanks again.

[ColinBarber]

1 hour ago, LeoSteve said:

So it seems like it's my error. If I let the car lock itself, I need to unlock with the remote 👌Thanks again.

The car shouldn't be randomly locking itself though. I wonder if the remote lock button is playing up and is randomly being 'pressed'? You could just take the Battery out for a few days to see if unprompted locking still occurs.