My tailgate glass wont open on my Touring (Wagon)

[320de46m47]

My tailgate glass wont open on my Touring (Wagon) and I suspect it's because the GMCU isn't coded right.
I don't want to pay 100 euros!!! (yes 20 second job and that's what theyre asking) to get it recoded when I might be wrong!

I know the motor and the lock work as when I bypass the relay it works fine

My question is ..how much current (and from where?) would need to be supplied to the relay trigger terminal if i bypass the gmcu?

it's pin 31 from plug x253 and it's a white and blue wire (RERHS) which goes to pin 4 on the relay. my gmcu is (i believe) not coded to supply an appropriate current so if i can find an alternative (live when the car is unlocked) and use the tailgate window switch to complete the circuit i should be in business

[320de46m47]

forgot to mention that i did change the relay too.
current to trigger passes along a 0.5 mm wire so needs to be very small

[320de46m47]

ive superimposed the trunk release switch diagram here and added a relay
the power to pin 4 on the tailgate glass relay is now supplied via the new relay 30 from the trunk release switch (small diagram). the relay is triggered by grounding 86 courtesy of the original switch supplied by ????? at 85??

[320de46m47]

the trunk release button supply (red line grey and red wire) is no good it dims the interior lights!

[320de46m47]

so i'm here now
just need a trigger current and a supply current
any suggestions appreciated