Icv constantly buzzing

[BMW_E30vert]

Hi car is a 1990 us spec 325i convertible(been converted from lhd to rhd)

The idle control valve is constantly buzzing regardless of ignition off/key out

i have swapped the main relay with a known working one but it still does the same, when the relay is removed the icv goes off

the ecu also seems to remain powered with the ignition off

oil pressure light stays on when ignition off/key out but goes off once ignition is turned on

i was advised it may be ignition switch, i swapped this with another but no joy(the original switch was red i swapped this with a white colored one)

I have another working 325i so can interchange parts to rule them out

This problem is really annoying as it drains my battery overnight

any advice on what to look for or test?

[Brianmoooore]

Ignore the other stuff and concentrate on the oil pressure light.
Pull the wire off of the pressure switch. What happens?.
Touch the pin of the plug to BODY earth. What happens?
Check out the engine to body earth strap.

[BMW_E30vert]

Was hoping you would see this Brian, the engine to body earth strap was grimy with oil and the protective layer was torn exposing wire i put insulation tape on this but i think i will change it, is there only one i.e from the sump to the chassis rail?

[Brianmoooore]

That's the one, but there is also a possibility of a poor connection between the alloy mount and the engine block. Never seen this on an E30, but have on other vehicles, and the alloy/iron sandwich means that the possibility is there.
Quick check is to connect a jump lead from the battery negative terminal on the RH turret to the engine lift bracket at the front of the engine.

[HairyScreech]

What do you define as buzzing?

If you listen closely to it with the engine off but electrics on then it will buzz as the ICV is energized.