So here's one for the electronics experts:

Whenever I use the IID Tool to check for fault codes and then do a 'clear all' various lights on the dash go on and off and the sat nav screen turns off and on again. There is also a whirring noise from underneath the car (sounds as if it is behind me).

So my question is does anyone know what is making the whirring noise?

Prompting the question is that every now and again I feel the car hesitate and sometimes this coincides with the 'HDC not available' message popping up then disappearing to leave the little delta and exclamation mark symbol which clears on the next restart.

EXCEPT for one time recently when the HDC message popped up then after a few minutes I heard the same whirring noise as mentioned above and the HDC message associated exclamation mark instantly disappeared! One and only time I've seen it do that. 2008 MY Java Black TDV8 HSE

How's your battery? The HDC fault message is the number one indicator of a poor battery and/or alternator.

Could the whirring noise be the in tank fuel pump? Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

Battery is tip top. Its a fairly new LR AGM technology version and I give it a full charge every now and again with CTEK MX5.0. So don't think it is the usual battery problem. 2008 MY Java Black TDV8 HSE

Hi there, could the whirring noise be the disc in the Nav DVD player underneath the passenger seat?

Thanks for the suggestion but would say it is not the sat nav as I'm familiar with that noise and it is better described as a series of clicks with a very subdued whirr.

The sound I hear on the clearing of DTCs is more like a servo motor running. Top suspect is the transfer box motor which I believe has two functions in that it drives the range changes and also the multiplate clutch for the centre differential. 2008 MY Java Black TDV8 HSE

Yes when you clear the faults or do a flash update then the car is rebooted, what you can hear is indeed the servo motors in the gearbox, also the BCM make's a noise as well as the locks relays.

Flack

Thanks Flack, you may have just helped to make a bit of a breakthrough on this fault I've been chasing for over 2 years!

So it seems the fault might be caused by a servo motor somewhere in the gearbox (or transfer box?).

What isn't clear is whether the fault is the servo in the gear/transfer box or if it is one of the control modules.

I just made contact with what seems like a fairly well clued-up electronics diagnostic specialist locally and they talked about making a logical step-by-step check of the CAN BUS and using oscilloscopes so might be possible to narrow it down a bit further. 2008 MY Java Black TDV8 HSE