Buyer Research

2021 Audi A4 — Should You Buy One?

Typical asking price: $22,000–$30,000. There is 1 high-severity known issue you need to know before handing over a check.

Deciding between model years? Compare the 15 Audi A4 years we've written up →

Kestrel Take

Eleven complaints is not a reliability rating — it is eleven people, and it tells you almost nothing about how the typical 2021 A4 is holding up. What the record does hold is four recalls, two of them worth taking seriously (a rear axle lock nut that can break and a rear camera that can go blank), plus a small run of 2025 reports of the digital instrument cluster crashing to a red triangle and leaving the driver without a speedometer. The car is the same 2.0T mild-hybrid B9 as the 2020, so read that year's page too: the MMI reboot wave that hit 2020s in 2025 has not shown up here in numbers, but the hardware is the same. Confirm all four recalls closed on the VIN, watch the cluster and the centre screen through the whole test drive, and buy on that basis — not on the short list.

What we checked

Checked against public records, 2026-09-25

NHTSA holds 11 owner complaints for the 2021 Audi A4, and 4 recall campaigns.

That is too small a record to read a pattern from, so we are not going to pretend otherwise — with numbers this low one owner moves the percentage by a lot. What has been filed is grouped under electrics and electronics (3), the transmission and drivetrain (2), lane departure (2). Treat those as things to look at, not as the vehicle's known weaknesses. A thin file usually means few of these were sold or few owners filed. It is not evidence the vehicle is trouble-free, and the issues below are our own research rather than a reading of this record.

4 recall campaigns cover this model year. Recalls are repaired free, for any owner, with no time limit on most safety campaigns — but only if someone books it in. Ask the seller to show it was done, or have any dealer check the VIN; it takes them a couple of minutes and costs nothing.

Counts come from the NHTSA complaint and recall database — free, public, and worth checking yourself.

Known Issues for the 2021 Audi A4

Ranked by wallet impact. These are documented, recurring problems — not freak accidents. How we decide that.

Rear axle lock nuts can break and throw the rear axle out of alignment (two recalls)High — wallet impact

Recall 21V295 covers 2020–2021 A4 sedans and Allroads: a rear axle lock nut can fracture, letting the axle shift and causing a loss of control. Dealers replace the lock nuts and any bolts that need it. Recall 22V034 followed for the same cars — misalignment from the same fault wears the rear tyres unevenly, so dealers inspect, realign and replace any tyres already ruined, free. The NHTSA VIN lookup should show both closed. If either is open, do not drive it home until the dealer has done the work; and check the inner shoulders of the rear tyres either way.

Repair cost: $0 with the recall — verify it was performed

Source: 4 NHTSA recall campaigns on this model year.

Digital instrument cluster crashes to a red triangle — speedometer and gauges gone while drivingMedium

Five of the eleven complaints, filed in 2025, describe the same thing: the virtual cockpit screen behind the wheel tries to boot, shows a red warning triangle, and crashes again, so the driver has no speed, fuel or warning readouts. Owners point to an Audi instrument-cluster campaign on other 2021 models that the A4 was not included in; we cannot confirm coverage, so ask a dealer to check this VIN for any open cluster campaign before you assume it is on you. Out of warranty the cluster is a dealer-only module with coding. On the test drive, watch the cluster from the moment the ignition comes on until you park — a flicker or a restart is the symptom.

Repair cost (estimate): $1,200–$3,000

Source: NHTSA complaints filed under electrics and electronics (3), lane departure (2).

Rearview camera display can go blank — infotainment software (recall)Medium

Recall 22V742 covers the 2021 A4 sedan and Allroad among most of the 2021 Audi line: a software fault in the infotainment unit can leave the rear camera display blank when reversing. The remedy is a free software update at the dealer. Confirm it on the VIN lookup, then check it yourself: shift into reverse three or four times during the visit and make sure the image comes up promptly each time and stays up.

Repair cost: $0 with the recall — verify it was performed

Source: NHTSA complaints filed under the driver-assist and automatic braking systems (2); 4 NHTSA recall campaigns on this model year.

Shudder and vibration at low speed from the seven-speed dual-clutch gearboxMedium

Two owners describe a humming, shuddering vibration in tight low-speed turns and a trembling, high-revving, jerky first-and-second-gear feel in stop-and-go traffic, one at only 13,000 miles. On the S tronic dual-clutch that pattern usually means clutch-pack judder or the mechatronic unit, and it is not a thing that fixes itself. Two reports is not a trend, but it is cheap to check: do a slow parking-lot figure-eight and a crawl in traffic, and feel for shudder through the floor on take-off. Ask whether the DSG fluid and filter were done at the 40,000-mile service.

Repair cost (estimate): $400–$2,500 depending on whether it is a fluid service, a clutch pack or the mechatronic unit

Source: NHTSA complaints filed under the transmission and drivetrain (2).

Middle rear seat belt retractor may not lock a child seat (recall)Low

Recall 21V606 covers the 2021 A4 among a long list of VW-group cars: the centre-rear seat belt's automatic locking retractor may not engage, so a child seat belted in with it can come loose in a crash. Dealers inspect and replace the belt assembly free. It only matters if you will carry a child seat in the middle seat, but it should still show closed on the VIN lookup. To check it yourself, pull the middle belt all the way out and let it retract — it should ratchet as it goes back in.

Repair cost: $0 with the recall — verify it was performed

Source: 4 NHTSA recall campaigns on this model year.

Walk-Away Red Flags

✗Instrument cluster flickers, restarts or shows a red triangle at any point
✗Backup camera comes up late or stays black in reverse
✗Shudder through the floor pulling away from a stop or in a tight slow turn
✗Inner edges of the rear tyres worn down while the outer tread looks new
✗Any recall still showing open on the NHTSA VIN lookup

Good Signs

✓All four recalls closed on the VIN lookup, with the rear axle inspection on a dealer invoice
✓Cluster and centre screen stayed lit and steady for the whole test drive
✓DSG fluid and filter service at 40,000 miles with a receipt
✓Rear tyres wearing evenly with an alignment printout in the file
✓Backup camera image up within a second every time you selected reverse