VVT solenoid testing

I have the code 644 which relates to camshaft timing out, so am trouble shooting in order... So far camtiming has been double checked (just had belt done) and from what Ive read so far ... to test the solenoid which sits on the rear cam (exhaust), when unplugged, the solenoid should show app 3.7 ohms resistance, BUT, just tried mine and its continous circuit, no resistance.

Obvious kinda question but presume mine is knackered?!

Anyone got a price on them? Mine is B5234T3 engine

Thanks