Model Reports 4 min read Updated 18 Oct 2026

Mercedes-Benz B-Class 2019: reliability & common MOT faults

In 2025, 89 in every 100 first MOTs on a 2019 Mercedes-Benz B-Class were passes. Most common reason for a fail: Tyre condition (front).

Summary

A 2019 Mercedes-Benz B-Class passed first time about 2 in every 100 more often than the average of the 2018 and 2020 model years.

At a glance

How 4,149 first tests went in 2025.

Passed first time
89 in every 100
Did not pass first time
11 in every 100454 failed first-attempt tests
The typical car
6 yearsabout 32,945 miles
First tests counted
4,149

What failed most often

  1. Tyre condition (front)20 in every 100 failed tests
  2. Airbag warning light12 in every 100 failed tests

How we count this. Data: UK MOT open data, 2025. Only Class 4 cars on their first MOT of the year are counted. A car that fails and is fixed at the test station still counts as a fail in the first-attempt rate. These are raw results, not adjusted for age, mileage, or peer mix. The MOT does not test engine or gearbox internals.

Note:

These are patterns across 2019 Mercedes-Benz B-Class vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.

Seat belts and restraints

One fault: airbag warning light, 11 times as often as on similar cars.

Figures below are measured across the 454 failed first attempts in 2025 that had a mileage recorded, which allows a like-for-like comparison.

We only list faults with at least 20 failures and a rate of about 2.0 times that of similar cars, which keeps one-off results out of the list.

Airbag warning light

Failed on 55 first tests11 times as often as similar carsLikely evidence

What it means

The airbag warning lamp (SRS MIL in DVSA's wording) is failed only if it indicates a system malfunction, which is Major. A lamp lit to show the passenger airbag is disabled is not to be regarded as a defect. Dashboard messages are not a defect in their own right, though they can help the tester confirm a malfunction.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Suspension

One fault: suspension arm ball joint (front), 3.3 times as often as on similar cars.

Suspension arm ball joint (front)

Failed on 24 first tests3.3 times as often as similar carsPossible evidence

What it means

A suspension arm ball joint is failed under the general suspension pin, bush or joint wording. Excessively worn is Major, and likely to become detached is graded Dangerous.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 23 first tests, 8.0 times as often as on similar cars.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.

MOT pass rates

How first tests ended, and how the pass rates are counted.

Passed first time
89in every 100
Passed on the first test.
Fixed at the station
2in every 100
Failed, then fixed at the test station the same day.
Failed
9in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 89.1% of 4,149 first tests (2025): only cars that passed first time count. Official-style pass 90.8%: cars fixed at the test station also count as a pass. The 2 fixed and the 9 not fixed make the 11 in every 100 that did not pass first time.

Petrol and diesel

First testsTypical mileagePassed first time, as testedPassed first time, same mileage
Petrol2,63430,690 miles9090
Diesel1,51537,073 miles8888

Figures are in every 100 first tests. Cars with more miles usually fail more often, so the same-mileage figure gives every fuel the mileage mix of all the cars in this year.

Same model, other years

Passed first time in every 100, all tested in 2025.

4060801002005201020152019Older carsNewer cars
40608010020102019Older cars

Newer cars are younger, so look for a jump rather than the climb.

YearPassed first timeFirst tests
200553 in every 100309
200656 in every 1001,552
200755 in every 1002,116
200855 in every 1002,936
200958 in every 1003,849
201058 in every 1004,152
201158 in every 1003,257
201269 in every 1005,571
201371 in every 1006,793
201471 in every 1007,934
201576 in every 1005,481
201679 in every 1005,183
201780 in every 1005,502
201883 in every 1003,858
2019 This car89 in every 1004,149
202090 in every 1002,786
202192 in every 1001,727
202291 in every 1001,216

If you are buying one

What this year's MOT record means for the decision in front of you.

Mileage makes a modest difference on a 2019 B-Class.

Of 2019 B-Class vehicles with under 21,000 miles, 92 in every 100 passed their 2025 MOT first time. With 48,000 miles or more, 85 in every 100 did.

Under 21,000860 tests
92
21,000–29,000808 tests
91
29,000–37,000 Typical car802 tests
90
37,000–48,000836 tests
87
48,000 and over843 tests
85

Petrol or diesel?

Typical mileagePassed first time,
as tested		Passed first time,
same mileage
Petrol30,690 miles9090
Diesel37,073 miles8888

Figures are in every 100 first tests. Petrol cars look better on the raw figures only because diesel cars have done more miles (typically 37,073 against 30,690). At the same mileage there is no clear difference between the two.

What to check at your mileage

How often each fault turned up on a failed first test, by the car's mileage. Read it as: what is likely to need looking at on a car like the one in front of you.

Under 21,00029,000–37,00048,000 and over
Tyre condition (front)2.01.93.1
Airbag warning light1.21.11.8

Faults per 100 first tests, by the car's mileage at the test.

When a car fails

66in every 100

of failed cars had one item to fix.

10in every 100

of failed cars had three or more items to fix.

3in every 100

of all first tests had a defect the tester marked dangerous (unsafe to drive away).

Every figure here is a first-attempt MOT rate from DVSA open data for this model line, for cars of this model year tested in 2025. Each mileage band holds a fifth of the tests. MOTs do not test engine or gearbox internals, so this is a pre-purchase checklist, not a full reliability score.

FAQs

Short answers about how to read this model-year guide.

A 2019 Mercedes-Benz B-Class passed first time about 2 in every 100 more often than the average of the 2018 and 2020 model years. In 2025, 89.1% of 4,149 first MOTs on the 2019 Mercedes-Benz B-Class passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 90.8%. Among 454 failed first-attempt MOT tests (test year 2025), Airbag warning light appears more often than on similar cars (12.1% of those tests; 55 observed failures; about 11× more often than similar cars). There is no single reliability score here; this is a pre-purchase checklist built from DVSA open data, not a guarantee for any individual car.
Ranked by how often they were actually recorded, the items that most often failed a 2019 Mercedes-Benz B-Class at the first attempt were Tyre condition (front) (19.6%) and Airbag warning light (12.1%), each as a share of the year's failed first attempts. That is what goes wrong most often on the car. The common faults table shows a different measure: faults that are unusual compared with similar cars.
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Airbag warning light (12.1% of those tests; 55 observed failures; about 11× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Airbag warning light shows up more often than on similar cars (12.1% of those tests; 55 observed failures; about 11× more often than similar cars). That does not prove a design fault. Age, mileage, and how the car was used still matter. Treat it as a pre-purchase checkpoint, not a manufacturer service bulletin.
Common MOT problem areas for the 2019 Mercedes-Benz B-Class include Airbag warning light, Suspension arm ball joint (front). These are the faults that stand out compared with similar cars, not a complete list of what can go wrong on any individual car.
This page highlights MOT failure patterns for the 2019 Mercedes-Benz B-Class (registration year) using UK DVSA open data for the selected test year. Patterns are compared with cars of a similar age and mileage. It is a buyer checklist from MOT defect statistics, not a full service history or manufacturer service-bulletin list.
No. MOT tests do not cover engine internals, gearboxes, or many electronic modules. Patterns here come from MOT defect statistics only and should not be read as engine or gearbox reliability scores.

About this data

How this page is built and what it can (and can't) say.

These figures come from UK MOT open data for this model year. We surface common failure patterns against similar cars, not a full reliability score, and not a pass/fail verdict on any individual vehicle.

2024 2025

What we include

UK Class 4 cars only. Normal MOT tests (not retests); first test per vehicle per calendar year; results pass, PRS, or fail.

Same-day repairs

PRS means the car failed items that were fixed at the test station and then passed the same day. We count PRS as a first-attempt fail in headline rates so same-day repairs do not hide problems.

How we compare

We compare this model year with other Class 4 cars of similar age and mileage in the same test year. This model family is left out of the peer group so the car is not measured against itself.

What this does not cover

  • MOTs do not cover engine internals, gearboxes, or many electronics; this is not a full reliability score.
  • Common faults come from MOT defect stats, not manufacturer TSBs or recalls.
  • Age and mileage matching reduces, but does not remove, differences in how cars were used and maintained.
  • If the data for a car is too thin to say anything useful, we say so rather than guess.

Contains public sector information licensed under the Open Government Licence v3.0.

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