Mercedes-Benz B-Class MOT Failure Rate & Common Faults
We analysed 73,356 MOT tests on the Mercedes-Benz B-Class carried out in 2023. 27% failed at the first attempt, which is slightly below the 29% average across all cars in the same data. Put another way, about 7 in 10 B-Classes passed first time.
Results cover cars first registered from 2005 to 2021. Compared with other cars of the same age, 2013 models did best (75% passed, +6.9 points against the average for 10-year-old cars), while 2011 models fared worst (61%, −1.5 points). Tested cars had covered 65,236 miles on average, against 73,145 across all cars.
The most common reason for failure was lights and electrics, found on 9.9% of tests (roughly in line with the 11.3% seen across all cars). The single most frequent fault was "fractured or broken", on 3.6% of tests.
- MOT tests analysed
- 73,356
- First-time pass rate
- 73%
- All cars: 71%
- Versus all cars
- +1.9 points
- Average mileage at test
- 65,236
- All cars: 73,145
Checking a particular B-Class?
See its own MOT history, advisories and mileage for free.
B-Class MOT pass rate by year
Older cars fail more often, so each year is compared with all cars of the same age. Bars above the dashed line did better than average for their age.
| First registered | Tests | Pass rate | All cars, same age | Difference | Avg mileage |
|---|---|---|---|---|---|
| 2021 | 71 | 94% | 91% | +3.5 points | 17,956 |
| 2020 | 3,016 | 91% | 88% | +3.1 points | 18,974 |
| 2019 | 4,317 | 90% | 86% | +4.0 points | 23,121 |
| 2018 | 3,985 | 87% | 84% | +2.7 points | 31,258 |
| 2017 | 5,748 | 84% | 82% | +2.3 points | 40,697 |
| 2016 | 5,378 | 83% | 79% | +4.5 points | 48,376 |
| 2015 | 5,708 | 80% | 75% | +4.8 points | 56,754 |
| 2014 | 8,371 | 75% | 72% | +3.6 points | 65,519 |
| 2013 | 7,210 | 75% | 68% | +6.9 points | 71,765 |
| 2012 | 5,969 | 71% | 66% | +5.2 points | 78,513 |
| 2011 | 3,781 | 61% | 63% | −1.5 points | 78,557 |
| 2010 | 4,889 | 60% | 60% | −0.0 points | 84,911 |
| 2009 | 4,781 | 59% | 59% | −0.2 points | 91,705 |
| 2008 | 3,939 | 56% | 57% | −0.9 points | 96,881 |
| 2007 | 3,174 | 56% | 57% | −1.1 points | 99,427 |
| 2006 | 2,476 | 56% | 56% | −0.0 points | 100,346 |
| 2005 | 539 | 56% | 56% | +0.0 points | 102,538 |
Why the Mercedes-Benz B-Class fails its MOT
The share of tests with at least one failure in each area, compared with all cars.
| Failure area | B-Class | All cars |
|---|---|---|
| Lights and electrics | 9.9% | 11.3% |
| Suspension | 8.3% | 8.9% |
| Tyres | 6.8% | 6.3% |
| Brakes | 6.1% | 6.8% |
| Visibility | 4.0% | 4.8% |
| Body and structure | 3.0% | 3.5% |
| Noise, emissions and leaks | 2.9% | 3.1% |
| Seatbelts and airbags | 1.5% | 1.0% |
| Road Wheels | 0.7% | 0.4% |
| Steering | 0.4% | 1.8% |
Top 10 specific failure reasons
- 1fractured or broken3.6%
- 2not working3.5%
- 3ball joint dust cover no longer prevents the ingress of dirt2.4%
- 4ball joint excessively worn2.2%
- 5inoperative or indicates a malfunction2.1%
- 6constant velocity boot split or insecure, no longer prevents the ingress of dirt2.0%
- 7has a cut in excess of the requirements deep enough to reach the ply or cords1.7%
- 8inoperative in the case of a single lamp or all lamps1.7%
- 9less than 1.5 mm thick1.7%
- 10tread depth below requirements of 1.6mm1.6%
Common B-Class MOT advisories
Advisories don't cause a fail, but they show what's wearing out. On a used B-Class, check whether these have been dealt with. Read our guide to MOT advisories.
| Advisory | Area | Share of tests |
|---|---|---|
| tread depth below requirements of 1.6mm | Tyres | 13.8% |
| has a tear, caused by separation or partial failure of its structure | Tyres | 9.5% |
| in such a condition that it is seriously weakened | Brakes | 7.7% |
| less than 1.5 mm thick | Brakes | 7.6% |
| excessively corroded | Brakes | 7.6% |
| significantly and obviously worn | Brakes | 3.2% |
| ball joint excessively worn | Suspension | 2.6% |
| Child Seat fitted not allowing full inspection of adult belt | Non-component advisories | 2.5% |
| has a cut in excess of the requirements deep enough to reach the ply or cords | Tyres | 2.3% |
| corroded so that its cross sectional area is reduced and seriously weakened | Suspension | 2.3% |
Tips to help your B-Class pass
Based on where B-Classes most often fail. For a full list, use our pre-MOT checklist.
Lights and electrics · 9.9% of B-Class tests
Walk round every light
With a helper, check headlights on dipped and main beam, sidelights, brake lights, indicators, the rear fog light and the number plate lamp. Replace blown bulbs in pairs and make sure no lenses are cracked.
Brakes · 6.1% of B-Class tests
Don't ignore brake warning signs
Grinding, squealing, a soft pedal or the car pulling to one side under braking are all worth investigating before the MOT. Check whether the last test noted worn pads or discs; if so, they may now be below the limit.
Compare with other models
Is the B-Class ULEZ compliant? See the Mercedes-Benz B-Class ULEZ check, or view all Mercedes-Benz models.
Other Mercedes-Benz models
Models with similar pass rates
About this data
Based on 73,356 first MOT tests of the Mercedes-Benz B-Class carried out in 2023.
Source: DVSA anonymised MOT test data (contains public sector information licensed under the Open Government Licence v3.0). First attempts on cars only; “pass rate” means passing first time. Averages cover all 32,735,164 cars tested (71% passed), and years with under 50 tests are hidden.
Learn more about how our data works.
Frequently asked questions
Answers from 73,356 first MOT tests of the Mercedes-Benz B-Class.
What is the Mercedes-Benz B-Class MOT failure rate?
In our data, 27% of 73,356 first MOT attempts on the Mercedes-Benz B-Class ended in a fail, compared with 29% for all cars.
What is the most common reason a Mercedes-Benz B-Class fails its MOT?
The most common failure areas were lights and electrics (9.9% of tests), suspension (8.3% of tests), tyres (6.8% of tests).
Which B-Class year has the best MOT pass rate?
Allowing for age, 2013 cars performed best: 75% passed first time, +6.9 points against the average for 10-year-old cars. The weakest was 2011, at 61% (−1.5 points).
How many miles had a typical Mercedes-Benz B-Class covered at its MOT?
The average was 65,236 miles, against 73,145 for all cars tested. 2021 cars averaged 17,956 miles and 2005 cars 102,538.
What is the most common MOT advisory on the Mercedes-Benz B-Class?
"tread depth below requirements of 1.6mm" was recorded on 13.8% of tests, in the tyres area. 6.8% of B-Classes failed in that area too.
How can I check a specific B-Class's MOT history?
Enter its registration in our free MOT check. Across the 73,356 B-Classes in our data, first-time pass rates ranged from 56% to 94% by year, so one car's own record says more than the average.
Related guides
- MOT · 6 min readPre-MOT checklist: 20 things to check yourself before the testTwenty quick checks, grouped by area, that you can do on your driveway in under half an hour. No tools beyond a coin and a helper needed for most.Read the guide
- MOT · 6 min readThe most common reasons cars fail their MOT (and how to avoid them)Lights alone failed 11.3% of cars at their 2023 MOT, more than any other area. The common failure areas, ranked, and the driveway checks that prevent them.Read the guide
- MOT · 4 min readTyre tread depth and the MOT: the legal limit and how to check6.3% of cars failed their 2023 MOT on tyres. The 1.6mm legal limit, what testers look for beyond tread, and a one-minute check with a 20p coin.Read the guide
Check any B-Class's MOT history
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