Problem with beeping noise in Lexus RX 400H

[Lawrence Cook]

For the first time half a mile into our journey an alarm sign came on similar to the seat belt warning noise and stayed on for the remaining 6 miles to home , no warning lights and everything checked ok , following day another short journey of 5 miles and same noise yet stopped a mile into the return journey, then set off to local garage to get it checked over journey of 8 miles no alarm so garage could not assess return journey of 8 miles complete silence , any advise or ideas would be appreciated, love the car and first problem to have had 

[mikesands]

I can't imagine what would trigger a noise with no warning symbol in the display, but my guess (ignoring that) would be a flakey switch on something like the parking brake, or the detection system in the front passenger seat for the seat belt use.

Mike

[jpjsavage]

We had a constant beeping a few days ago, and I found out it was because the back seats were not fully locked into position. Someone had accidentally touched the switch in the boot and they had move a little bit from their normal locked position.