look under the RH side around the middle of body and you'll see the modulator, it has 2 solenoids on top, one on a side and the transducer on the other which is the most common culprit but as it's not very cheap it's better to confirm the fault with a tester....see this
www.discovery2.co.uk / ACE amber light - Pressure Transducer and the attachment, also you can isolate a bit the fault if you can identify the behaviour of the car while the warning is on i mean it's in "locked bars" or "floppy" condition cos according to that you can reduce the "range" of faults... if you dont have one download a RAVE and read
Workshop manual - Front suspension - ACE description and operation - Failure modes and you'll understand ... check here Disc 1
land rover rave technical system , if it doesnt work try here
http://www.landroverresource.com/docs/D2_Workshop_Manual.pdf