Tyre Pressure Warning thingy wont go off

[X5-D-Sport]

Hi People - 2004 E53 D-Sport vehicle.

I have a warning icon on the instrument panel - tyre profile shape with Exclamation mark in middle lit in RED.
This lit up a mile after blowing the tyres up to 33psi all round the other day - like I do every couple of weeks to check.

I have tried using the service reset OBD tool, but cannot clear it.

The ABS works as it should & proved this the other day on shallow mud...

Any clues as to WHY this is illuminated even after 1200 miles.... and how do I clear it plz ?

Regards
Grant B

[marti]

Press the button in the centre console with the same symbol on, where your PDC , hill decent and heated seat buttons are it will or should turn amber and then after driven a short distance should go off.....why 33psi alround mine were different front to back...why does it come on??...because one of your tyres is losing pressure.

[X5-D-Sport]

I had a replacement set of tyres - I have matching rear rims all round, & was thinking one of the old tyres was about 5psi low & this changed the rolling diameter possibly, as the tyres were blown up to 33 after change... as this is the pressure I normally run on all 4 tyres, & allows it to run without uneven wear on fronts or rears.
I get about 15k+ motorway driving out of a set, & some times swap fronts to rears occasionally to keep them wearing perfectly evenly.

I am presuming the gentle pressure drop on one tyre was ignored by the car, but when that suddenly changed by additional 5psi when tyres changed, that nudged the computer into reacting maybe ?