Any E-TS (Attesa) Guru here? have some issues with my R32

[youask]

Hi!
My R32 GT-R has developed a 4wd light 

I've done some error finding and need to have some input

If i start the car i get the 4wd lamp in the cluster and errorcode 18 (18 – ETS pressure switch or circuit)

I've tested the pressure switch and it's normally closed to earth when car is off and if I run the pump manually via the relay in the boot the switch goes to open so the switch seems to work. The pump does not sound bad and builds pressure within a 1-2sec from cold and makes the switch go to open state

If i run the pump for more than 1-2sec it changes sound from a normal pump sound to something that sounds like a hising/overflow sound so that seems ok

I can actually get the 4wd to work if i manually run the pump for 1-2sec , then set the ignition to on and starts the car

Can it be a bad nitrogen canister?

I've checked all power and earth to the box and solenoid/motor system and it's all fine