Goalkeeper Johansen defied Dale Stephens to prevent City falling 2-1 behind immediately after Jack Redshaw’s spot kick was saved, then stopped Ryan Brooke’s bid to make the score 3-3.
Kieran Trippier, who had filled an unfamiliar role at left back for the young Blues, stepped up to confirm a 4-2 win at a cold Regional Athletics Arena after team-mates James Poole, Paul Marshall and John Guidetti all netted.
Midfielder Michael Johnson, continuing his welcome return to full fitness after long-term injury, played the first half in comfortable style before Glyn Hodges replaced him with Guidetti.
Johnson, who scored in the 5-1 Carling Cup win over Scunthorpe, had City’s best chance against Oldham but his shot was well saved by Dean Brill after fine work from Javan Vidal and Redshaw.
Dedryck Boyata almost crowned a good defensive performance by nicking an unlikely winner from 35 yards with a rising shot that just cleared Brill’s bar with almost half an hour gone.
City were probably watched by as many coaches as there were scouts - Eddie Niedzwiecki, Brian Kidd and Scott Sellars were in the stand as well as Hodges and Andy Welsh on the bench.
But they found chances few and far between, and Oldham threatened in the second half with Stephens’ dipping free kick and a free header that substitute Tom Eaves directed over the bar.
Yet when it came to keeping their nerve, City won through for their second Senior Cup victory in the round-robin stage following last month’s comprehensive 5-1 effort against Stockport.
Shoot-out details: Poole 1-0, Lee 1-1, Redshaw saved 1-1, Stephens saved 1-1, Marshall 2-1, Black 2-2, Guidetti 3-2, Brooke saved 3-2, Trippier 4-2.
