Ohio State trailed by as many as 17 in the first half but got within five points on Washington’s layup with 51.7 seconds left in the first.
After the teams traded 3-pointers in the last minute, Illinois took a 40-35 lead into halftime.
The Buckeyes cut the deficit to two twice in the first six minutes of the second half, but Illinois responded with a 10-1 run to extend the lead back to 11.
Again, Ohio State rallied.
With 7:59 to go, Walker drove to the hole for a layup and got fouled. His ensuing free throw cut the deficit to one at 61-60.
Washington tied the game at 65 with a 3-pointer just before the six-minute mark, and Walker put the Buckeyes on top with a short fadeaway jumper in the lane 25 seconds later.
Illinois responded with a 7-0 run to go back in front by five, the last three on a shot by Trent Frazier.
Washington stopped the spurt with a driving layup, but Dosunmu answered with a deep 3-pointer from the top of the key to extend the lead back to six.
It wasn’t enough.
Ohio State rallied one more time with Sueing tying the game with an old-fashioned three-point play with 23 seconds left and Liddell preserving the tie by swatting a put-back attempt by Cockburn was the clock ticked down.
Washington gave Ohio State an 81-80 lead with a layup with 2:47 left, but Cockburn erased that with a pair from the charity stripe and Illinois was able to hang on.
Ohio State was in the Big Ten Tournament final for the first time since beating Wisconsin in the 2013 edition. That was the end of a run in which the Buckeyes made it to the final five years in a row.