OBD diagnostics · purchase protection

2021 Audi A4
Common Problems & Inspection Guide

Verify baseline vehicle system stability data. Learn what to check on the physical vehicle computer before signing a bill of sale.

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Platform Heritage

The Audi A4 is a line of luxury compact executive cars produced from 1994 to 2025 by the German car manufacturer Audi, a subsidiary of the Volkswagen Group. The A4 has been built in five generations and is based on the Volkswagen Group B platform. The first generation A4 succeeded the Audi 80. The automaker's internal numbering treats the A4 as a continuation of the Audi 80 lineage, with the initial A4 designated as the B5-series, followed by the B6, B7, B8, and the B9. The B8 and B9 versions of the A4 are built on the Volkswagen Group MLB platform shared with several models and brands across the Volkswagen Group. The Audi A4 automobile layout consists of a front-engine design, with transaxle-type transmissions mounted at the rear of the engine. The cars are front-wheel drive, or on some models, "quattro" all-wheel drive. The A4 is available as a sedan and station wagon. Historically, the second (B6) and third generations (B7) of the A4 also included a convertible version. For the B8 and B9 versions, the convertible, along with a new coupé and 5-door liftback variant, was spun-off by Audi into a new nameplate called the Audi A5. It has been manufactured in Ingolstadt since its beginning, in Changchun China by FAW-VW since 2003 and in Aurangabad India by Audi India since 2007. The B9 generation A4 and A5 will be replaced by B10 version of A5, as part of Audi's new naming convention.

Source: Wikipedia intro extract · as of Jun 19, 2026

Key facts for this model year

11NHTSA owner complaints
4Safety recalls on file
2Top issue reports · Electrical System
$0Typical OEM recall remedy cost to you

~2.3k average monthly buyer searches in the US (google ads data · as of Jun 19, 2026). Run a MotoMetrics scan for your VIN to see live repair exposure.

Verify the data — open primary sources · as of Jun 19, 2026

System Defect Summaries & Field Data

Active safety recalls on file: 4 (source: NHTSA Recalls API · as of Jun 19, 2026)

Top NHTSA complaint categories

Recent recall summaries

Campaign 21V606000 · SEAT BELTS:REAR/OTHER:RETRACTOR · API record

Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2021 Volkswagen ID4, Audi A4 Allroad, A4 Sedan, A5 Cabriolet, A5 Coupe, A5 Sportback, A6 Allroad, A6 Sedan, A7, A8, E-Tron Quattro, E-Tron Sportback Quattro, Q3, Q5, Q5 Sportback, Q7, Q8, RS5 Sportback, RS5 Coupe, RS6 Avant, RS7, RSQ8, S4 Sedan, S5 Cabriolet, S5 Coupe, S5 Sportback, S6 Sedan, S7, S8, SQ5, SQ5 Sportback, SQ7, SQ8, and 2021-2022 S3 Sedan vehicles. The rear seat belt automatic locking retractors may deactivate early, which can prevent the child restraint system from securing properly. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 208, "Occupant Crash Protection."

Campaign 22V034000 · TIRES · API record

Volkswagen Group of America, Inc. (Audi) is recalling certain 2019-2021 Audi A5 Sportback, RS5 Coupe, RS5 Sportback, S5 Sportback, 2020-2021 A4 Allroad, A4 Sedan, A5 Cabriolet, A5 Coupe, A6 Allroad, A6 Sedan, A7, A8, Q5, S4 Sedan, S5 Coupe, S5 Cabriolet, S6 Sedan, S7, S8, SQ5, 2021 Q5 Sportback, Q7, Q8, RS6 Avant, RS7, RSQ8, SQ5 Sportback, SQ7, and SQ8 vehicles. The rear axle alignment may not have been inspected after the repairs for Recall 21V-295 (42L1) were performed.

Campaign 21V295000 · SUSPENSION:REAR:AXLE:NON-POWERED AXLE ASSEMBLY · API record

Volkswagen Group of America, Inc. (Audi) is recalling certain 2021 Q7, Q8, Q5 Sportback, SQ5 Sportback, RS6 Avant, RS7, RS Q8, 2020-2021 Audi S6 sedan, Q5, A8, S8, A7, A6 Allroad, A5 Cabriolet, A4 sedan, A4 Allroad, SQ5, S7, A6 sedan, S5 coupe, S4 sedan, S5 Cabriolet, A5 coupe, 2019-2021 RS5 coupe, A5 Sportback, S5 Sportback, RS5 Sportback vehicles. The lock nut on the trailing arm of the rear axle may break due to stress corrosion.

Campaign 22V742000 · BACK OVER PREVENTION:DISPLAY FUNCTION · API record

Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2021 Audi A8, RS7, RS6 Avant, RS5 Sportback, RS5 Coupe, Q8, Q7, Q5 Sportback, S4 Sedan, Q5, A7, A6, A6 Allroad, A5 Sportback, A5 Coupe, A5 Cabrioleet, A4 Sedan, A4 Allroad, E-Tron Sportback Quattro, SQ7, S5 Cabriolet, E-Tron Quattro, SQ8, SQ5 Sportback, SQ5, S8, S7, S6 Sedan, S5 Sportback, S5 Coupe, 2022 E-Tron GT, and 2021-2022 RSQ8 vehicles. Due to a software issue, a blank or black screen may be displayed instead of the rearview camera image when the vehicle is placed in reverse gear. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 111, "Rear Visibility."

YouTube voice themes below are research hints only — verify against NHTSA data before citing.

Search demand cross-check: ~2,334 avg monthly intent searches (source: google ads data · as of Jun 19, 2026)

On-Site Audi A4 Pre-Purchase Checklist

  1. Verify OBD-II readiness monitors are complete (not recently cleared) using a full protocol scan.
  2. Compare dashboard mileage to ECU-stored odometer modules where accessible.
  3. Pull permanent and pending DTCs — not only stored codes visible on the dash.
  4. Inspect systems related to ELECTRICAL SYSTEM (NHTSA complaint cluster — verify during test drive and PPI).
  5. Inspect systems related to TIRES (NHTSA complaint cluster — verify during test drive and PPI).
  6. Inspect systems related to POWER TRAIN (NHTSA complaint cluster — verify during test drive and PPI).
  7. Inspect systems related to UNKNOWN OR OTHER,LANE DEPARTURE,FORWARD COLLISION AVOIDANCE (NHTSA complaint cluster — verify during test drive and PPI).
  8. Inspect systems related to ELECTRICAL SYSTEM,LANE DEPARTURE,FORWARD COLLISION AVOIDANCE (NHTSA complaint cluster — verify during test drive and PPI).
  9. Confirm recall remedy completed for SEAT BELTS:REAR/OTHER:RETRACTOR (campaign 21V606000).
  10. Confirm recall remedy completed for TIRES (campaign 22V034000).
  11. Confirm recall remedy completed for SUSPENSION:REAR:AXLE:NON-POWERED AXLE ASSEMBLY (campaign 21V295000).
  12. Run a MotoMetrics on-site scan for Audi A4 before signing the bill of sale.

Alternative Inferences & Cross-Shopping Matrix

Adjacent model years for this nameplate and equivalent footprints shoppers compare across brands.

Generational cohorts

2018 Audi A4

Class competitors

2021 Bmw 5 Series 2019 Bmw 3 Series 2019 Bmw 5 Series 2018 Audi A6 2018 Bmw 3 Series 2018 Bmw 5 Series 2018 Bmw 550I

Vehicle health varies wildly by individual history. Aggregate recall and complaint data cannot tell you whether the specific car on the lot had its monitors cleared or its odometer rolled back. Verify the physical or digital scan before you sign a bill of sale.

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