Umtiti was on hand seven minutes from time to score with a deflected shot, restoring parity after Edinson Cavani's first-half header to add to the home side's indifferent form.
Despite their unbeaten opening to the campaign, a run of three consecutive draws in all competitions is likely to lead to further speculation surrounding Blanc's position at the club, with fans growing increasingly frustrated at a perceived sluggish start to their title defence and in Europe.
They were given a good contest by visiting Lyon, who threatened to make a breakthrough before Umtiti's strike before half time when Arnold Mvuemba's free-kick cannoned back off the woodwork.
The hosts thought they had earned a win at the death when Marco Verratti headed home late on, but the Italian's effort was ruled out for an earlier foul.
Despite Blanc facing criticism in the build-up to this match, he would have been pleased with his side's early efforts at the Parc des Princes.
The hosts had an appeal for a penalty turned down after 12 minutes, when Blaise Matuidi's cross appeared to come off the arm of Bakary Kone, before Yohan Cabaye latched onto Zlatan Ibrahimovic's flick-on inside the box and fired wide.
Alexandre Lacazette nearly responded for the visitors on 25 minutes, but drilled harmlessly wide, before Mvuemba rattled the crossbar five minutes later with a curling free-kick from just outside the box.
Umtiti recovered from the uncertainty to strike the crucial blow with six minutes left. PSG totally failed to clear a corner and the France Under-21 defender's scuffed effort deflected off Serge Aurier and past a helpless Salvatore Sirigu.
