They looked to be heading to defeat deep into injury time until striker Luke Rodgers headed home.
Crewe had started brightly showing some crisp passing through midfield and it created two early half chances.
Steve Jones produced one excellent early flick to put Eddie Johnson through but the on-loan player's touch was too strong and it allowed Andrew Whing to cut in and make a timely interception.
But it was all heavy going in the early stages with neither side capable of turning possession into anything truly threatening.
David Vaughan produced the first effort at goal in the 18th minute but his shot went wide of the mark.
Michael Doyle then followed suit with a left-foot shot which failed to trouble Ross Turnbull in the Crewe goal.
The game needed something to lift it and Don Hutchison provided it in the 32nd minute.
A Coventry corner was cleared as far as Isaac Osbourne who controlled it well and fed Gary McSheffrey.
The striker saw the veteran Hutchison making a late run and delivered the perfect cross allowing him to turn the ball home from close range.
The former Scotland international could have had another a minute later when his shot was deflected wide.
He then turned provider just before half-time when he cleverly lobbed the ball forward for strike partner Dele Adebola but the former Crewe man shot just over the top.
Crewe again began the second period brightly with Jones and Vaughan both having shots blocked.
Their cause was aided when Coventry midfielder Doyle managed to get himself booked twice inside 30 seconds for dissent.
The sending off seemed to spark more urgency into the home side who were unlucky when James Scowcroft had a shot hit the post and bounce out.
Things swung Crewe's way when Robert Page was carried off leaving Coventry to play out 10 minutes with only nine men.
They looked to have survived but in the final 60 seconds of the six minutes of injury time Rodgers headed home to earn a draw.
After the match referee Paul Melin had to be escorted off the pitch after a fan had invaded the field.