Fuel level sensor calibration (uc10/nsp)

Hi, Im having an issue with the calibration of the fuel level sensor. Brand new PHR sensor for supra mk4.

I have an haltech r3 + UC10, sender is wired directly to the dash (sensor ground and avi 1, internal pullup 240 ohm enabled). I watched the haltech ressources and tutorials.

My issue is that the voltage when I have the key ON and when the car is running is totally different therefore my calibration is false.

For example, 30 liters in the fuel tank ,key ON position= 1,46v , when the engine is running I have 0,86v.

Any advice ?

Thanks !