"We're extremely close to having a start date for the trams, we're working through the final kinks," the minister told reporters on Thursday.
Mr Knoll said major mistakes were made when underground signalling systems were installed.
"As we've been saying all along, the ongoing issues with the tram extension relate to an issue with the signalling system - which was installed way back in January," he said.
"Labor buried this problem underground in January and now we know they have effectively buried up to $44 million along with it."
But opposition transport and infrastructure spokesman Tom Koutsantonis said Mr Knoll was out of his depth.
"You've all seen Mr Knoll come up with another excuse about the tram delay, trying to blame everything on Labor after the premier announced a no excuses government." Mr Koutsantonis said.
"All we're getting from the minister is excuses. The truth is they have over promised and they can't deliver.
"They promised that they would get this done and they've wrecked it."
The new tram line links an existing service to the site of the old Royal Adelaide Hospital with a spur also taking passengers to the nearby Festival Centre.
It drew criticism after it was first announced when it was revealed trams would be unable to turn right from King William Street into North Terrace with the then Labor ruling the extra infrastructure needed too expensive.
The Liberals went to the March state election promising to add a right turn but are yet to outline when they will deliver on their commitment.