The defender turned in a Fisayo Dele-Bashiru cross to give Man City a 40th-minute lead before 16-year-old Jayden Braaf doubled the home side's advantage on 51 minutes.
Billy Gilmour pulled a goal back for Chelsea on 82 minutes, scoring a penalty after substitute Faustino Anjorin had been fouled.
Chelsea captain Guehi levelled from close range to put the Blues on seven points from three matches and above second-placed Arsenal on goal difference.
Man City, in 10th place, earned their first point of the campaign.
Man City: 31 Aug v Liverpool (A)
Chelsea: 30 Aug v Spurs (H)