Had a brain fart Yesterday, left my lights on and the battery went flat in my (JDM) 2006 Toyota Avensis. Normally there would be warning chime but didn't seem to register in my mind that day somehow. Anyway, Got a jump start from a workmate in the afternoon and was on my way home. I took the battery out and recharged it overnight to top it up.

In the morning, put the battery back in and started my car and drove to work as per normal and it appears to be starting first time each time okay so far today. However every time I park and turn off the motor, there is a periodic beeping sound (Similar to an old Casio watch sound) every 5 seconds coming from around under the dash / steering wheel and it doesn't go away. Turn the ignition into the On position and the beeping will disappear. it doesn't sound like the normal warning chimes for leaving the lights on or leaving the keys in the ingntion while door is open. There's no warning lights illuminated on the dash once the engine is started.

Even with the keys out of the ignition, everything turned off, doors are all shut, the beeping remains and doesn't appear to ever stop.

Does anyone know what this is and what is it trying to notify me of? if it's a battery fault? Cheers