Record crowds had followed the two time Major Champion around Golfclub München Eichenried on day one and he continued to take a bumper following with him as he moved to 11 under.
South African Christiaan Bezuidenhout carded the lowest round of the week with a 65 to emerge as the nearest challenger, one shot clear of Finnish playing partner Kim Koivu and Swede Sebastian Soderberg.
Defending champion Matt Wallace was then part of a group of seven players four shots back.
Kaymer’s last European Tour victory came at the 2014 U.S. Open Championship but the German is beginning to show signs of the form that made him a Race to Dubai Champion and World Number One.
The 34-year-old claimed the second of his 11 European Tour wins at this event 11 years ago and he was delighting the home crowds again over the first two days in Munich.
“The support inspires, it’s different,” he said. “Sometimes you feel embarrassed. It’s a lot to handle at certain times because I’m not that kind of guy that likes to be in the spotlight – but it’s a positive thing and I need to see it as something positive.
“It’s going to be exciting for sure. It’s never easy leading a golf tournament but fortunately I’ve done it a few times in my career.
“It’s a very nice position to be in. Now I just play against myself, try to reach my number and hopefully it’s enough to be in the lead on Saturday evening.
“I didn’t play as well as yesterday, especially on the first nine, I wasn’t comfortable in the way I was hitting the ball. I missed a lot of shots right but I was scrambling well. I felt something nice in my swing and from the 11th I played really well.”
He endured a roller coaster start with two birdies and two bogeys in his opening four holes but got on the green at the par five sixth in two to turn in 35.
A birdie on the 11th in similar fashion then triggered a hat-trick of gains as he holed a spectacular bunker shot on the next and put an approach to four feet at the 13th to share the lead.
He holed from 14 feet on the 15th to hit the front on his own and then holed from similar range on the last after getting up and down from the drop zone over the green.
Bezuidenhout – who made a birdie and a bogey as he finished his first round early in the morning – went birdie-bogey from the second but then made a gain on the sixth and added four in a row from the eighth to leap up the leaderboard.
Another birdie from 20 feet on the 13th handed him the solo lead and when he took advantage of the last from 12 feet, he was nine under.
Koivu was picked up a birdie in finishing his first round and then made gains on the first, fifth and sixth to turn in 33.
He was still five under for the week stood on the 15th tee but birdied the 15th, 16th and last to catapult himself up the leaderobard.
Soderberg was bogey free in his 67, making birdies on the 13th, 18th, second, third and eighth.
Wallace carded a 68 with six birdies and two bogeys to get to seven under alongside fellow Englishmen Jordan Smith and Lee Westwood, Italian pair Edoardo Molinari and Andrea Pavan, home favourite Max Schmitt and Spaniard Alvaro Quiros.
India’s Gaganjeet Bhullar won a BMW M8 coupé worth €194,000 as he holed a six iron from 196 yards on the 17th for the 16th hole-in-one of the season.
European Tour Release