The high pressure EAS tank is located under the frame rail just forward of the Range Rover fuel tank. This resovior holds approximately 2.5 US gallons(9.7L) of compressed air at 150 PSI(10 bar). The pressure contained within this tank should not be treated lightly and the utmost care should be used when interacting with this system.
Read and clear this fault code yourself with the EAS Unlock V4 for the P38 Range Rover.