Model Reports 4 min read Updated 18 Oct 2026

Mercedes-Benz CLS 2017: reliability & common MOT faults

In 2025, 80 in every 100 first MOTs on a 2017 Mercedes-Benz CLS were passes. Most common reason for a fail: Tyre condition (front).

Summary

The 2017 Mercedes-Benz CLS follows the pattern of the model years either side.

At a glance

How 1,415 first tests went in 2025.

Passed first time
80 in every 100
Did not pass first time
20 in every 100288 failed first-attempt tests
The typical car
8 yearsabout 64,332 miles
First tests counted
1,415

What failed most often

  1. Tyre condition (front)25 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 2017 Mercedes-Benz CLS 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.

Noise, emissions and leaks

One fault: diesel engine warning light, 3.4 times as often as on similar cars.

Figures below are measured across the 288 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.

Diesel engine warning light

Failed on 30 first tests3.4 times as often as similar carsLikely evidence

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.

Tyres

Three wear patterns. The strongest is the tyre tread depth (rear): 3.3 times as often as on similar cars.

Tyre tread depth (rear)

Failed on 32 first tests3.3 times as often as similar carsWear pattern

What it means

Only primary grooves count when tread depth is assessed: those holding the wear indicators, or cut as deep as those when new. Shallower secondary grooves are ignored. Tread depth below the minimum for the vehicle is Dangerous, and so is a pattern not visible over the whole tread, but that second row applies only to vehicles that need the lower minimum.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 57 first tests, 2.0 times as often as on similar cars.

Tyre condition (front)

Failed on 72 first tests2.8 times as often as similar carsWear pattern

What it means

Exposed or damaged ply or cords are graded Dangerous. A cut in excess of the requirements and deep enough to reach the ply or cords is Major, and testers may open the cut with a blunt instrument to check its depth. A tyre contacting the vehicle through flexing or suspension movement is not a defect; fouling fails only at the time of test.

Tyre condition (rear)

Failed on 51 first tests2.3 times as often as similar carsWear pattern

What it means

Exposed or damaged ply or cords are graded Dangerous. A cut in excess of the requirements and deep enough to reach the ply or cords is Major, and testers may open the cut with a blunt instrument to check its depth. A tyre contacting the vehicle through flexing or suspension movement is not a defect; fouling fails only at the time of test.

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
80in 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
18in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 79.6% of 1,415 first tests (2025): only cars that passed first time count. Official-style pass 82.2%: cars fixed at the test station also count as a pass. The 2 fixed and the 18 not fixed make the 20 in every 100 that did not pass first time.

Same model, other years

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

406080100200520102017Older carsNewer cars
40608010020102017Older cars

Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 79 in every 100 passed first time.

YearPassed first timeFirst tests
200571 in every 100799
200670 in every 1001,098
200767 in every 1001,373
200869 in every 1001,128
200966 in every 100895
201065 in every 100927
201173 in every 1001,026
201274 in every 1001,012
201371 in every 1002,809
201474 in every 1001,644
201578 in every 1002,729
201679 in every 1002,000
2017 This car80 in every 1001,415
201883 in every 100900
201982 in every 1001,002

FAQs

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

The 2017 Mercedes-Benz CLS follows the pattern of the model years either side. In 2025, 79.6% of 1,415 first MOTs on the 2017 Mercedes-Benz CLS passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 82.2%. Among 288 failed first-attempt MOT tests (test year 2025), Diesel engine warning light appears more often than on similar cars (10.4% of those tests; 30 observed failures; about 3.4× 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 2017 Mercedes-Benz CLS at the first attempt were Tyre condition (front) (25.0%), 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: Diesel engine warning light (10.4% of those tests; 30 observed failures; about 3.4× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Diesel engine warning light shows up more often than on similar cars (10.4% of those tests; 30 observed failures; about 3.4× 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 2017 Mercedes-Benz CLS include Diesel engine warning light. 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 2017 Mercedes-Benz CLS (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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