Used car guide

2021 BMW 120D M Sport Auto: common problems and what to check

What gets flagged at MOT on 2021 BMW 120D M Sport Autos, from 188 tests in 2025, plus known faults and what to look at before you buy one.

Small sample: only 188 of these were MOT tested in 2025, so treat the percentages as rough. The known faults below don't depend on it.

188MOT tests in 2025
90%pass first time (all 2021 cars: 87%)
9,700typical miles a year
28%had tyres flagged

What gets flagged at MOT

The share of 2021 BMW 120D M Sport Auto MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Tyres
    28% 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
    9% 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.

  • Wipers, windscreen and mirrors
    2% of testsRough price £15–£250

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

  • Suspension
    2% 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
    1% of testsRough price £80–£250

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

  • Lights and electrics
    1% of testsRough price £10–£80

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

Known faults

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 warning light faults
    All engines

    The main faults reported are electrical: warning lights with no clear cause and infotainment faults.

    At the viewing: Test the screen and check no warning lights stay on.

    Source: What Car?: used BMW 1 Series (2019 on) reliability

  • Particulate filter warnings (diesel)
    Diesel

    Diesels have more problems, including DPF warnings and engine management faults.

    At the viewing: Ask what journeys it does, and watch for warning lights.

    Source: What Car?: used BMW 1 Series (2019 on) reliability

  • Airbag and camshaft recalls (2020)
    Some cars

    Recalls covered the driver's airbag fabric (about 1,100 cars) and camshaft bearing cap screws that could come loose (39 cars).

    At the viewing: Ask a BMW dealer to confirm the recalls were done.

    Source: What Car?: used BMW 1 Series (2019 on) reliability

Looking at a BMW 120D M Sport Auto?

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Other years

YearMOT testsMost flagged
2022140Tyres 15%

Where this comes from: the DVSA's anonymised results for every MOT test in Great Britain in 2025, counting tests of 2021 BMW 120D M Sport Autos registered in 2021. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score