McIlroy shot the round of the day to haul himself back into the mix after receiving a two-shot penalty Thursday for improving his lie on a hole where he made a double-bogey.
"I'd much rather be two shots worse off than be called a cheat," said McIlroy, reflecting on the incident at the 12th hole during his opening round at Yas Links.
"I made peace with it and at least I went out today and it wasn't playing on my mind. I had a clear conscience and I could just go and play."
The six-time major champion carded a nine-under 63 in round two, picking up seven birdies on the back nine to bolster his chances of winning a record-equalling eighth Race to Dubai title.
"It wasn't like I got off to the greatest of starts today, but then obviously I got it going," said McIlroy, who overcame a bogey on the first hole before finding his groove.
"I went out today and played a good round of golf and did get myself back into the tournament," he added. "I've given myself a great chance."
Rahm is level at the top on 12-under with Tyrrell Hatton and overnight leader Francesco Laporta in his first event since leaving the rebel LIV Golf tour, which has announced it will shut down after five contentious years.
The Spaniard began the day three shots off the pace but climbed into a tie for the lead with a five-under 67.
Laporta left the door ajar with an inconsistent two-under 70 in his second round, as Hatton shot a seven-under 65 to reel in the Italian alongside close friend Rahm.
