Used car guide

2020 BMW 3 Series diesel: common problems and MOT failures

What MOT testers find on the diesel BMW 3 Series first registered in 2020 (diesel cars only): we looked at the 7,118 MOTs these cars had during 2023–2025. Plus known faults and what to look at before you buy one.

7,118MOTs of 2020 diesel cars, done in 2023–2025
85%pass first time (all 2020 cars: 87%)
9,800typical miles a year
3.5×the usual rate for engine warning light

What goes wrong more than usual on a 2020 BMW 3 Series diesel?

Parts flagged at MOT more often on the 2020 BMW 3 Series diesel than on all cars registered in 2020.

  • Engine warning light3.5× usual
    BMW 3 Series
    2.1% All 2020 cars
    0.6%

    Failed outright at MOT: 2.1%, against 0.6% of all 2020 cars. The rest were advisories or minor defects.

    Rough price £10–£80 our estimate

    At the viewing: Ask a friend to check every light while you work the switches: indicators, brake lights, fog lights and reversing lights.

Better than most

Brake discs: 3.1% here, against 7.3% of all 2020 cars.

Common 2020 BMW 3 Series diesel MOT failures and advisories

The share of 2020 BMW 3 Series diesel MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Tyres
    27% of testsRough price £70–£150

    At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.

  • Brakes
    12% of testsRough price £150–£350

    At the viewing: Look for a lip on the disc edges and feel for judder or pulling when braking firmly from about 40mph.

  • Lights and electrics
    3% of testsRough price £10–£80

    At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.

  • Wipers, windscreen and mirrors
    3% of testsRough price £15–£250

    At the viewing: Check for chips in the driver's view, and test the wipers and washers.

  • Suspension
    3% of testsRough price £120–£400

    At the viewing: Listen for knocks over speed bumps, and look behind each front wheel for a snapped coil spring.

  • Seats and seatbelts
    2% of testsRough price £80–£250

    At the viewing: Pull each seatbelt sharply. It should lock, and retract cleanly.

Known faults on the 2020 BMW 3 Series diesel

Reported by owners, mechanics and buying guides for this model and age. Check which engine the car has, as some apply to one engine only.

  • Electrical and infotainment glitches

    All engines

    In What Car?'s survey 13% of petrol and plug-in hybrid cars had a fault, mostly minor electrical, engine and infotainment glitches.

    At the viewing: Test the infotainment and all the electrics, and make sure no warning lights show.

    Source: What Car?: BMW 3 Series (2019 on) reliability

Questions to ask the seller before buying a 2020 BMW 3 Series diesel

Ask before you travel to see it. A seller who knows the car will have answers, and receipts.

  1. Any recent work on the engine warning light? (Flagged at MOT 3.5× as often on the 2020 BMW 3 Series diesel as on other cars the same age.)
  2. Can I see the service history and receipts for any big jobs?

Looking at a BMW 3 Series?

Check the actual car: its own MOT history, mileage and what to ask the seller. Free, no sign-up.

Other years

Every year of the BMW 3 Series compared

YearMOT testsMost flagged
2026–Too new for MOT data
2025–Too new for MOT data
2024–Too new for MOT data
2023–Too new for MOT data
2022–Too few tests
2021759Tyres 21%
201934,846Tyres 25%
201825,493Tyres 26%
201710,906Tyres 26%
201673,403Tyres 27%
201591,029Tyres 28%
201490,046Tyres 30%
201397,821Tyres 30%
201296,040Tyres 32%
201181,787Tyres 33%
201075,455Suspension 35%
200967,536Suspension 37%
200866,671Brakes 40%
200777,186Brakes 41%
200657,039Brakes 46%
200536,334Brakes 46%
200427,771Brakes 44%
200329,361Brakes 44%
200222,806Brakes 42%
200114,634Brakes 43%
20007,767Brakes 43%
19997,370Brakes 38%
19985,623Suspension 35%
19974,172Brakes 36%
19962,941Brakes 37%
19951,929Brakes 37%
19941,187Brakes 34%
19931,172Brakes 32%
19921,287Suspension 28%
19911,968Suspension 26%
19903,254Suspension 25%
1989–Too few tests
1988–Too few tests
1987–Too few tests
1986–Too few tests
1985–Too few tests
1984–Too few tests
1983–Too few tests
1982–Too few tests
1981–Too few tests
1980–Too few tests
1979–Too few tests
1978–Too few tests
1977–Too few tests
1976–Too few tests

Where this comes from: the DVSA's anonymised results for every MOT test done in Great Britain during 2023–2025, counting the MOTs of BMW 3 Series cars first registered in 2020. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score