19 problems have been reported for the 2021 Audi A4. The following chart shows the 10 most common problems for 2021 Audi A4. The number one most common problem is related to the vehicle's electrical system with 4 problems. The second most common problem is related to the vehicle's equipment (3 problems).
| Problem Category | Number of Problems |
|---|---|
| Electrical System | |
| Equipment | |
| Forward Collision Avoidance | |
| Power Train | |
| Suspension | |
| Lane Departure | |
| Tire | |
| Air Bag | |
| Engine And Engine Cooling | |
| Vehicle Speed Control |
In our research we use the PPMY index to compare the reliability of vehicles. The PPMY index of a certain model is defined as the problems reported per thousand vehicles per Year. The total sales of the 2021 Audi A4 in the United States are 16,688 units [1]. If the total number of problems reported by Audi A4 owners in the last 4 years is 19, and the age of the vehicle is 4, the PPMY index can then be calculated as
PPMY Index = 19 / 16,688 / 4 * 1000 = 0.28.
For more information, refer to this page: A study of reliability comparison across Audi A4 model year vehicles.
The following chart shows the number of problems reported during each of the service years since the debut of the 2021 Audi A4 in 2021.
| Service Year | Number of Problems |
|---|---|
| 2025 | |
| 2024 | |
| 2023 | |
| 2022 | |
| 2021 |
When making the decision between buying a new or used Audi A4, the following table can be used to compare the 2021 Audi A4 with the Audi A4 from other model years. Note that the number of problems reported for the 2021 A4 is 19 while the average number of problems reported for the 29 model years of the Audi A4 is 126.