It was one of three Hitachi class 385 electric trains taken off commuter routes earlier in October after an issue with the brake control system was detected.
ScotRail said Hitachi has sorted the matter and the trains can get back into service.
The first train, seven-carriages long, was operating between Edinburgh and Glasgow via Falkirk High on Saturday.
The remaining two trains are expected to return to service next week, ScotRail said.
The fault, which “led to a small loss of signalling across the brake network cables” was identified on Thursday October 4, ScotRail said.
The operator said the train had remained safe as the overarching brake control was not affected and that the driver was in control of it at all times.
Hitachi is now said to have applied a modification to fix the fault, which it will apply to all of the class 385 trains.
In July, ScotRail said there were due to be 70 of the new class 385 electric trains running in the central belt by early next year.
Alex Hynes, ScotRail Alliance managing director, said: “I am pleased that Hitachi has resolved the issue with the class 385 train, and that we can get it back into service for our customers.
“There can sometimes be difficulties when introducing a brand-new fleet, but it’s great that customers will once again be able to benefit from these modern electric trains.”
Andy Radford, programme manager for Hitachi Rail, added: “We know that passengers really enjoy the space, comfort and the extra seats that the new trains offer.
“We’re pleased to have been able to fix the issue - having our engineers move quickly to find a solution, test, and introduce it.
“The modern electric trains can now resume carrying people smoothly between Edinburgh and Glasgow.”