At a glance
How 1,536 first tests went in 2025.
- Passed first time
- 81 in every 100
- Did not pass first time
- 19 in every 100298 failed first-attempt tests
- The typical car
- 6 yearsabout 60,998 miles
- First tests counted
- 1,536
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.
These are patterns across 2019 Mercedes-Benz X-Class vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. A wear pattern follows age and use more than the way the car was built. 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, 16 times as often as on similar cars.
Figures below are measured across the 298 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
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.
Tyres
One wear pattern: tyre pressure monitoring system, 3.7 times as often as on similar cars.
Tyre pressure monitoring system
What it means
A tyre pressure monitoring system that is obviously inoperative is graded Major, and so is one listed as malfunctioning or obviously inoperative. The Minor row uses the word malfunctioning too, but its detail is a warning lamp indicating a fault, and it also covers a tyre that is obviously under-inflated.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
Noise, emissions and leaks
One fault: diesel engine warning light, 3.4 times as often as on similar cars.
Diesel engine warning light
What it means
An engine malfunction indicator lamp that is illuminated to show a malfunction is graded Major on a diesel, but only on the diesels the test covers, which depends on the vehicle type and when it was first used. DVSA lists it under exhaust emissions for compression ignition engines, and the detail line for the row also names an inoperative lamp.
Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.
MOT pass rates
How first tests ended, and how the pass rates are counted.
- Passed first time
- 81in every 100
- Passed on the first test.
- Fixed at the station
- 3in every 100
- Failed, then fixed at the test station the same day.
- Failed
- 16in every 100
- Did not pass, and were not fixed at the test station.
First-attempt pass 80.6% of 1,536 first tests (2025): only cars that passed first time count. Official-style pass 83.6%: cars fixed at the test station also count as a pass. The 3 fixed and the 16 not fixed make the 19 in every 100 that did not pass first time.
Same model, other years
Passed first time in every 100, all tested in 2025.
| Year | Passed first time | First tests |
|---|---|---|
| 2018 | 80 in every 100 | 1,193 |
| 2019 This car | 81 in every 100 | 1,536 |
| 2020 | 86 in every 100 | 630 |
Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 80 in every 100 passed first time.
FAQs
Short answers about how to read this model-year guide.
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.
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.
Check any vehicle’s MOT history
Full MOT history, mileage records, and reliability insights for any UK vehicle.
Run a free check