The experienced former Queens Park Rangers and Sunderland man is being assessed by boss Ian Evatt with a view to landing a deal at the University of Bolton Stadium.
It is nearly 12 months since the 33-year-old last played competitively for the Black Cats but Evatt has been impressed with the kind of qualities Lynch could add to his squad as they bid to move towards the right end of League Two.
“We will monitor it day to day, possibly week to week,” he said.
“He is doing well. He needs to be fitter and sharper, he’ll admit that himself, but he has a lot of quality and has had a fantastic career.
“He brings a lot of things to the table that we don’t have a lot of, like leadership skills, a big strong character and a winning attitude.”
Having previously spent time training with fellow League Two side Southend, Lynch initially made the trip north last week.
His chances of a deal looked dead and buried after he left the North West at the weekend, with no planned return, but he was then invited back.
Fellow left-sided centre-half George Taft completed a move to Scunthorpe in January and Evatt is weighing Lynch up with Ryan Delaney and Reiss Greenidge already competing for that position.