E39 oil level sensor

[Brianmoooore]

Mid 2000 E39 2.8 touring, with a M52TU motor. Has the graphic display on the instruments, showing doors open, bulb failure, etc., but not the alpha/numeric 'check' display.
I've already found out the hard way that it doesn't have a coolant level sensor, when a hose partly pushed off, and I only found out when the temp. gauge began to climb.
The sump definitely has an oil level sensor in it, with wiring connected to it, but I've never seen any indication of low oil on the instruments, either when the oil level was known to very low (just below the bottom mark on the dipstick), or when the sump was completely empty during an oil change.
So is the oil level sensor there just to block up the hole in the sump, or is it faulty, and where is the indication of ow oil level on the instruments, if there is one.

[fixedwheelnut]

If it has one fitted then it should bring on the Oil warning light in yellow after starting and the red goes out.
Red for pressure/yellow for level
level has to be just below the minimum for it to come on [think approx 2mm below min on the dipstick]

[Brianmoooore]

Ah, very clever!
Swapped in another sensor (of unknown condition) from a spare engine, while the sump was empty, and tried the engine with just under five litres of oil. Red light went out, as always, but unfortunately not replaced by a yellow one.

[clipper]

Different engine I know (M54), but when I had a fairly major leak on my 525i facelift E39 the oil level light wouldn't come on util the oil was quite some way below the min level on the dipstick. So far below that 1 litre didn't bring it up to the dipstick mark.

No coolant level sensor is a pain, I found out that I was low on coolant the same way as you Brian, lucky there was no lasting damage as the needle went to the red in a space of seconds.....