2021 Audi A4 — MOT failures & pass rate
16,336 MOT tests on the 2021 Audi A4 are in this dataset, and 90.3% of them passed. Executive cars of a similar age fail at 9.8%, so the 2021 A4 sits squarely on the average. Failures cluster in tyres, lighting & signalling and visibility.
What the MOT record shows
Tyres dominates the failure mix at 7.2% of all tests — 6.0 points clear of lighting & signalling, so it is the first thing to check.
At component level the recurring items are tread depth, headlamp aim and malfunction indicator lamp — tread depth alone was recorded 472 times.
Mileage matters less than usual here: the 2021 A4 fails 7.6% of the time in the 0-30k band and 8.8% at 120-150k, a spread of only 1.2 points.
Fuel type barely separates them — petrol fails 9.2% of the time against 10.4% for diesel.
Advisories point at the next bill rather than this one: tyres was flagged on 22.9% of tests without failing them.
The trend is worsening — 7.8% of tests failed in 2023 against 9.8% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 7.2% | 1,178 |
| 2 | Lighting & signalling | 1.2% | 192 |
| 3 | Visibility | 1.1% | 175 |
| 4 | Emissions & environmental | 0.9% | 144 |
| 5 | Brakes | 0.8% | 131 |
| 6 | Suspension | 0.8% | 122 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Tread depth | 472 |
| 2 | Headlamp aim | 234 |
| 3 | Malfunction indicator lamp | 130 |
| 4 | Brake pads | 124 |
| 5 | Wipers | 117 |
| 6 | Shock absorbers | 101 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 22.9% | 3,732 |
| 2 | Brakes | 8.4% | 1,368 |
| 3 | Other defects | 7.0% | 1,145 |
| 4 | Suspension | 4.7% | 774 |
| 5 | Visibility | 3.2% | 521 |
| 6 | Road wheels | 0.4% | 61 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 5,976 | 7.6% |
| 30-60k | 8,351 | 10.8% |
| 60-90k | 1,619 | 11.2% |
| 90-120k | 315 | 14.0% |
| 120-150k | 57 | 8.8% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 8,858 | 9.2% |
| Diesel | 7,387 | 10.4% |
| Hybrid | 91 | 7.7% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2023 | 384 | 7.8% |
| 2024 | 8,095 | 9.7% |
| 2025 | 7,820 | 9.8% |
What to check before buying a 2021 A4
On a 2021 A4, tyres is what the MOT record says goes wrong most — it appeared in 7.2% of tests. Check these areas before you commit.
- Tyres (7.2% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (1.2% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Visibility (1.1% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£150.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2021 Audi A4s pass their MOT?
90.3% of the 16,336 2021 Audi A4 MOT tests in this dataset passed — a 9.7% fail rate.
What is the most common MOT failure on a 2021 Audi A4?
Tyres, recorded in 7.2% of tests, followed by lighting & signalling (1.2%).
Does the 2021 A4 get worse with mileage?
Its MOT fail rate rises from 7.6% in the 0-30k band to 8.8% in the 120-150k band.
Methodology & source. Based on 16,336 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.