Hoping somebody knowledgeable might be able to give me a simple explanation here:

Basically if I lock the car (2011, 4.4TDV8), leave it for more than about 5 to 10 minutes then unlock the car, the alarm siren sounds for a about 2 seconds, just the siren, not the horn, and the clock and date in the car reset themselves back to 12:00 01/01/2009. The car unlocks as normal and seems to be fine apart from this. Doesn't make any difference if I single lock, deadlock, unlock the whole car, just unlock the boot or use the spare key. If I lock and unlock in a quicker time frame it works fine, without the siren.

It started doing this intermittently a few months ago and the car regularly complained about battery charge after short journeys so I have since replaced the battery. Still does it with the new battery.

I initially assumed something motorised was stalling and drawing too much current, low voltage causing the alarm to go off but the door locks, boot lock, mirrors, retractable side steps etc all work perfectly on their own I have discounted this.

Current thinking is dying backup battery in the alarm siren? Is there such a thing in the RR? Does the system only arm the alarm after a few minutes?

Wouldn't mind getting to the bottom of it as its quite loud and embarrassing, plus its annoying having no idea what time it is.

Thank you! Current: 2011 RR 4.4 TDV8 Vogue SE
1986 LR 90 Recently Rebuilt
1958 LR S2 Ready for a rebuild!
Previous: 2007 RR 3.6 TDV8 Vogue SE

Assuming the new battery is still healthy and fully charged, I’d try a ‘hard’ reset if not tried already, disconnect both the positive and negative cables from the battery (after waiting 120 secs. from unlocking / opening the bonnet) and touch them together for a few seconds, then re-connect everything and see how you go 👍 Jonathan

2007 Defender 90 XS Hardtop

Thanks Jonathan, I will give it a try this afternoon and report back if it stops raining. I thought I had read that this only worked on the 3.6 so didn't think to try it. Current: 2011 RR 4.4 TDV8 Vogue SE
1986 LR 90 Recently Rebuilt
1958 LR S2 Ready for a rebuild!
Previous: 2007 RR 3.6 TDV8 Vogue SE

May or may not have any effect but it’s quick and free so worth a shot  Jonathan

2007 Defender 90 XS Hardtop

Disconnected the battery and performed a hard reset, no difference unfortunately.
Asked my mechanic to read the fault codes as I happened to be passing and apart from some presumably unrelated issues (issue with speaker 1 and 2 and a circuit issue with the EGR) there were also some on the body module: B1B01-87 Key transponder, B1087-88 LIN bus A and B12C9-88 LIN bus E. Guessing just a red herring but thought it worth mentioning. Current: 2011 RR 4.4 TDV8 Vogue SE
1986 LR 90 Recently Rebuilt
1958 LR S2 Ready for a rebuild!
Previous: 2007 RR 3.6 TDV8 Vogue SE

Some additional info: I have just replaced the battery in the Webasto pre heater remote fob. When I turn this on remotely this also causes the alarm siren to sound and the clock to reset. Current: 2011 RR 4.4 TDV8 Vogue SE
1986 LR 90 Recently Rebuilt
1958 LR S2 Ready for a rebuild!
Previous: 2007 RR 3.6 TDV8 Vogue SE