BMW 420d — MOT pass rate & failures
The BMW 420d recorded a 87.3% MOT pass rate across 240,913 tests in this dataset (model years 2013–2023), with tyres, lighting & signalling and brakes its most common failure areas. Its 12.7% fail rate is higher than the 11.8% average across all BMW 4 Series versions.
How it compares
By model year
| Year | Tests | Pass rate | Fail rate |
|---|---|---|---|
| 2013 | 2,786 | 83.6% | 16.4% |
| 2014 | 37,700 | 84.2% | 15.8% |
| 2015 | 46,547 | 86.1% | 13.9% |
| 2016 | 50,712 | 87.8% | 12.2% |
| 2017 | 49,617 | 88.7% | 11.3% |
| 2018 | 30,527 | 89.4% | 10.6% |
| 2019 | 14,626 | 88.4% | 11.6% |
| 2020 | 3,739 | 89.7% | 10.3% |
| 2021 | 3,160 | 88.2% | 11.8% |
| 2022 | 1,440 | 91.9% | 8.1% |
| 2023 | 59 | 93.2% | 6.8% |
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 7.5% | 18,104 |
| 2 | Lighting & signalling | 2.8% | 6,741 |
| 3 | Brakes | 2.3% | 5,570 |
| 4 | Visibility | 1.9% | 4,610 |
| 5 | Suspension | 1.7% | 4,127 |
| 6 | Road wheels | 0.8% | 2,013 |
| 7 | Emissions & environmental | 0.5% | 1,300 |
| 8 | Other defects | 0.5% | 1,145 |
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 | 7,566 |
| 2 | Brake pads | 4,162 |
| 3 | Washers | 3,565 |
| 4 | Headlamp aim | 3,340 |
| 5 | Shock absorbers | 2,709 |
| 6 | Headlamp | 1,954 |
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 | 23.1% | 55,589 |
| 2 | Brakes | 14.7% | 35,477 |
| 3 | Other defects | 9.0% | 21,622 |
| 4 | Suspension | 5.5% | 13,145 |
| 5 | Visibility | 3.1% | 7,364 |
| 6 | Emissions & environmental | 2.4% | 5,857 |
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 | 27,282 | 8.0% |
| 30-60k | 85,247 | 10.9% |
| 60-90k | 75,738 | 13.7% |
| 90-120k | 36,715 | 16.0% |
| 120-150k | 11,836 | 16.8% |
| 150k+ | 4,069 | 18.7% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 44,899 | 11.0% |
| 2022 | 47,717 | 11.7% |
| 2023 | 48,635 | 12.9% |
| 2024 | 49,659 | 13.6% |
| 2025 | 50,003 | 13.9% |
What to check before buying a BMW 420d
Focus on the areas it most often fails on — and remember MOT data covers testable defects only, not engine or gearbox health.
- Tyres (7.5% 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 (2.8% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (2.3% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
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 reliable is the BMW 420d at MOT time?
87.3% of the 240,913 BMW 420d MOT tests in this dataset passed — a 12.7% fail rate, in line with the 11.8% average across all 4 Series versions.
What is the most common MOT failure on a BMW 420d?
Tyres, recorded in 7.5% of tests, followed by lighting & signalling (2.8%).
Does the 420d get worse with mileage?
Its MOT fail rate rises from 8.0% in the 0-30k band to 18.7% in the 150k+ band.
Methodology & source. Based on 240,913 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-06. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.