Kunteng Controller Throttle Voltage ?

[Pegazus]

I just received my KT controller and I'm dealing with an issue regarding throttle.

Here is the link of the controller and the main caracteristics :

https://www.aliexpress.com/item/32819334542.html?spm=a2g0s.9042311.0.0.27426c37SRTiSx

Rated voltage 48V
Rated current 20A
Low voltage protection DC39±0.5V
Maximum current 40±1A
Speed set 1-4.2V
Brake input Low-level

Here is the throttle :

https://fr.aliexpress.com/item/1871145926.html?spm=a2g0s.9042311.0.0.27426c37SRTiSx

Regarding most wiring diagram of KT controller I understand that :
GND = 0 V
+ = 5 V
Signal = from 0 to 5V

From the controller spec I understand
1 V = 0% speed
4.2 V = 100% speed

But I mesure 4.2 V on the positive wire (red) coming from the controller and I can't get more than 4.2 - 0.8 = 3.4 V from the signal wire. That means I'm unable to reach top speed

Did you experience such thing, can you explain it or solve it ?

Thanks in advance !

 

[Pegazus]

I mesure PAS and brake positive voltage and I get more 4,2 or 4,6 V ...

Is there any way (potentiometer, resistance, ...) to tune this to get a real + 5 V ?