Kevin Davies had opened the scoring for the hosts, but the veteran striker was shown a straight red card towards the end of the match and the Sky Blues capitalised on their numerical advantage as Moussa produced a dramatic equaliser deep into time added on.
Preston dominated the first half and the best chance fell to Joe Garner, whose firm shot was brilliantly tipped over after he sped through on goal by Coventry goalkeeper Joe Murphy.
The Lilywhites broke the deadlock in the 53rd minute when David Buchanan's left-wing cross found Davies in the six-yard box and the latter side-footed into the roof of the net.
Davies ensured a nervy finish for the hosts when he was sent off two minutes from time for a high tackle on Cyrus Christie.
And, as the clash headed into the dying seconds, Moussa struck a stunning 35-yard volley into the top corner to snatch a point for the visitors.