Yaris 2001 digital sender problem

[Alexgr]

Hello there, so i have a 2001 yaris 1.4 diesel with stucked sender. I changed it to a Toyota dealer but the mechanic was little confused because the tank was half empty and the sensor showed 7/8 bars (with the new sender). Its really weird because I made more than 500 km from the last time I filled full the tank and it still shows 7/8 bars. Is there any possibility that the new sender doesn't work? 

[flash22]

Digital display ? you either have a wiring fault or a problem with the gauge

[Alexgr]

Hi, the mechanic disengaged the connection and the digital display showed no bars 0/8. The gauge is new

[flash22]

Is the car French or JAP built ?

[Alexgr]

Jap

[flash22]

The correct sender should be 83320-52061

[Alexgr]

Yes, I changed it yesterday in a toyota dealer garage 

[flash22]

It's possibly a bad ground on the sender circuit check the earth/ground to the engine block

[Alexgr]

The mechanic that changed the sender removed the Battery just in case. By the way, I went to a gas station and filled the tank. It needed 30L to fill therefore the new sender dosent show true reading. I will contact the toyota garage! 

[flash22]

Without testing the sender, how do you know it's the problem

[Alexgr]

I got no idea man, what is your suggestion ? I mean what should I do ? I have no idea how to check the earth/ground to the engine block