One problem related to automatic transmission control module has been reported for the 2018 Audi A3. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2018 Audi A3 based on all problems reported for the 2018 A3.
On February 19, 2022, I drove from my home in san francisco to the home depot in colma/daly city. This is a 7 mile drive one way on the freeway. When I was leaving the parking lot at the home depot, I put the car in reverse and all of a sudden it would not move. The car stopped. I turned the ignition off. Then on. There were no warning lights. I put the car in reverse again, and now it was bucking and stopped. It would not move. I had the car towed to my house on Saturday February 19, and again on Monday February 21 to the Audi of san francisco service department. The dealer told me that the problem was with the tcm (transmission control module). It needed a software upgrade. Wow. This is really dangerous. Imagine if I was on the highway going 65 mph and the tcm decided it needed a software upgrade. I am so happy I was in a parking lot. So, I always bring my car into the Audi service department. And they never upgraded the tcm software. They said it is not part of "maintenance". This is clearly wrong! and very dangerous. I am suprised that no on has been killed in an accident because of this. So, I paid: $250. Deductible plus $275. Diagnostic. Plus $570. For tcm software update ($1095. Total) invoice/order #944256. Chris, the service advisor reported to me that Audi of America does not require or recommend software updates to the tcm. And software updates are not part of the extended warranty. And also told me software is not covered under any warranty at Audi.