Full G train service returned Monday morning, following a major MTA summer project to modernize the line’s aging signaling system.

Construction on the project began on June 28, and involved three phases of service suspensions along the line, spanning from Brooklyn to Queens.

Service was halted in segments from Court Square to Church Avenue to replace the line’s outdated signal system.

MTA Chairman and CEO Janno Lieber at a press conference in mid-June went so far as to describe the control rooms at the Nassau Avenue station “the land that time forgot.”

Construction crews replaced that system with the latest in communications-based train control — otherwise known as CBTC technology — which the MTA touts as vital to making the G line more reliable for its 160,000 daily riders.

The project was budgeted to cost approximately $368 million, according to MTA officials.

Editor’s Note: A previous version of this story misstated the total cost of the project.