DTC B115C-7A: Transfer Fuel Pump - Fluid leak or seal failure: Action

NOTE: This DTC is set when the fuel level sensor values indicate that insufficient fuel is being transferred from the passive side of the fuel tank to the active side. It is common for drivers to report erratic changes in fuel gauge when this fault develops

Refer to the appropriate service information and check the transfer pump circuit for short circuit to ground, short circuit to power, open circuit, high resistance
Check the transfer hose for leaks and restrictions