Hello.
FMB140 reads fuel level from vehicles ECU, it doesn't calculate it.
We would like to anayze your issue deeper. Please create a ticket on VIP Helpdesk and provide all needed information in it:
Device IMEI, firmware version, GSM number, lvcangetinfo response, vehicle data: manufacturer, prod. year, connection manual that was used for installation.
If you don't have VIP Helpdesk account please ask your Sales Manager for help or If you don't have any contacts with our Sale managers, please contact with them on our official website
https://teltonika-gps.com/ and click on the "Contact Us" button. When you will click, please fill the form and submit it.
Note: as a topic, please choose "Vehicle telematics".
Or you can send an e-mail with description of your situation to info@teltonika.lt
Best Regards