Brazilian-born Ricardo Nascimento got his first start of the season after a lengthy injury layoff while Tiyani Mabunda started ahead of Hlompho Kekana on the day.
Sundowns shot-stopper Denis Onyango was put to the test in the opening exchanges, but the Ugandan international showcased his quality with strong reflexes.
Sundowns dusted off the slow start with the opener on the half-way mark as Gaston Sirino slotted home from the penalty spot after Themba Zwane saw his shot handled in the area.
Petro went close to drawing level on 33 minutes, but Onyango once again came up trumps with an excellent block to deny Picas.
The leveller duly arrived seven minutes later when Job stepped up from the spot to beat get the better of Onyango after Ngcongca was adjudged to have handled in the area.
Sundowns made an enforced change 12 minutes after halftime, as goalkeeper Onyango made way for Zambian shot-stopper Kennedy Mweene.
Motjeka Madisha, who was on the score-sheet in the reverse fixture, threatened to put his side back in front with a header off Sirino’s free-kick on 70 minutes but Barros parried clear.
Petro then took advantage and went ahead a minute later after Jacques Tuyisenge finished off a delivery from Picas with 19 minutes left in the contest.
However, the South African champions forced a point three minutes into added time when Madisha rose high to head home Sirino’s cross as Sundowns remain top in Group C.
Sundowns: Onyango, Madisha, Nascimento, Lebusa, Ngcongca, Jali, Mabunda, Zwane, Morena, Sirino, Vilakazi.
Subs: Mweene, Langerman, Arendse, Mahlambi, Mkhulise, Meza, Maboe.