Model Reports 8 min read Updated 12 Jul 2026

Mercedes-Benz Ml 2009: reliability & common MOT faults

Elevated MOT failure patterns for the 2009 Mercedes-Benz Ml include Decelerometer (sp) (~17.3× peers) and Side repeaters (~9.2× peers). Based on UK DVSA open data for test year 2025 (568 failed first-attempt tests), compared with similar age and mileage peers. Available test years: 2024, 2025.

568 failed first-attempt tests · 1,700 first tests (test year 2025)

Standout pattern: Decelerometer (sp) — about 17.3× more often than on similar peer cars.

Key takeaways before you buy

  • Decelerometer (sp): about 17.3× more often than similar cars
  • Side repeaters: about 9.2× more often than similar cars
  • Coil spring (rear): about 3.1× more often than similar cars

Common faults

These are MOT failure patterns that show up more often on this registration year than on similar cars of the same class, age band, and mileage in the same test year (leave-one-out peer comparison; whole model family excluded).

Statistical patterns from MOT defect codes — not manufacturer TSBs, recalls, or a diagnosis of any individual car. Fail and advisory patterns are kept separate.

Based on 568 failed first-attempt tests in test year 2025.

Decelerometer (sp)

This failure pattern appears about 17.3× more often than on similar peer cars — recorded on 30 failed first-attempt tests; 5.3% of failed tests for this model year.

Any · 30 failures · ×17.3 vs similar cars · 5.3% of failed first tests · Likely common fault pattern

Side repeaters

This failure pattern appears about 9.2× more often than on similar peer cars — recorded on 91 failed first-attempt tests; 16.0% of failed tests for this model year.

Any · 91 failures · ×9.2 vs similar cars · 16.0% of failed first tests · Likely common fault pattern

No patterns met the strongest callout thresholds on this page; showing the highest-lift rows that still cleared the display floors.

# Fault pattern Location Failures vs similar cars Share of fails Confidence
1 Decelerometer (sp)
Brakes > Brake performance > Parking brake efficiency (sp) > Decelerometer (sp)
 Any 30 ×17.3 5.3% Likely common fault pattern
2 Side repeaters
Lamps, reflectors and electrical equipment > Direction indicators > Flashing type > Side repeaters
 Any 91 ×9.2 16.0% Likely common fault pattern
3 Coil spring (rear)
Suspension > Springs > Coil springs > Coil spring
 Rear 71 ×3.1 12.5% Likely common fault pattern
4 Rigid brake pipes (rear)
Brakes > Rigid brake pipes
 Rear 26 ×2.6 4.6% Possible elevated fault
5 On or after 01/07/2008
Noise, emissions and leaks > Exhaust emissions > Compression ignition > On or after 01/07/2008
 Any 34 ×2.4 6.0% Possible elevated fault

Only patterns that clear minimum sample and elevation thresholds are shown (at least 20 failures and 2.0× peer lift).

Advisories

Advisory items recorded on failed first-attempt tests that appear elevated versus peers. Advisories are not a fail rate — they flag issues noted at the test, often before they become failures.

# Advisory pattern Location Notes vs similar cars Share Confidence
1 Rigid brake pipes (front)
Brakes > Rigid brake pipes
 Front 55 ×3.6 9.7% Elevated vs peers
2 Rigid brake pipes (rear)
Brakes > Rigid brake pipes
 Rear 67 ×2.5 11.8% Possible elevated fault
3 Engine oil leaks
Noise, emissions and leaks > Fluid leaks > Engine oil leaks
 Any 153 ×2.1 26.9% Elevated vs peers
4 Engine oil leaks (front)
Noise, emissions and leaks > Fluid leaks > Engine oil leaks
 Front 25 ×2.1 4.4% Elevated vs peers

FAQs

We do not show a single reliability score for the 2009 Mercedes-Benz Ml on this page. Among 568 failed first-attempt MOT tests (test year 2025), Decelerometer (sp) appears more often than on similar peer cars (about 17.3× more often than peers; 30 observed failures; 5.3% of failed tests). Treat this as a pre-purchase checklist from DVSA open data — not a guarantee for any individual car.
Among failed first-attempt tests we surface patterns that appear more often than on similar peer cars. Top example: Decelerometer (sp) (about 17.3× more often than peers; 30 observed failures; 5.3% of failed tests). These are statistical signals, not a diagnosis of any individual car.
Decelerometer (sp) shows up more often than on similar peer cars (about 17.3× more often than peers; 30 observed failures; 5.3% of failed tests). That does not prove a causal design fault — age, mileage, and usage still matter. Treat it as a pre-purchase check point, not a manufacturer TSB.
Common MOT problem areas for the 2009 Mercedes-Benz Ml include Decelerometer (sp), Side repeaters, Coil spring (rear). These are elevated versus similar peer cars where lift clears our floors — not a full list of every possible fault on an individual car.
Advisories flag issues noted at the test and are not a fail rate. We show advisory patterns that look elevated versus peers among failed first-attempt tests, separate from common failure rows. Use them as early-warning checks, not as a pass/fail score.
This page highlights elevated MOT failure patterns for the 2009 Mercedes-Benz Ml (registration year) using UK DVSA open data for the selected test year. Patterns are ranked against similar age and mileage peers. It is a buyer checklist from MOT defect statistics — not a full service history or manufacturer TSB 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.
PRS means the vehicle 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.

About this data

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

PRS policy. PRS means the vehicle 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.

Peer baseline. We compare this model year with other class 4 cars of similar age and mileage in the same test year, excluding the whole model family so the car is not compared with itself (leave-one-out peer baseline).

Data years. Test years covered: 2024, 2025.

Limitations.

  • MOT tests do not cover engine internals, gearboxes, or many electronic modules — so this is not a full reliability score.
  • Common faults are inferred from MOT defect statistics, not manufacturer TSBs or recalls.
  • Matching on age and mileage reduces but does not remove every usage or maintenance difference between cars.
  • Pass rates and star scores appear only when those data marts are available; this page never invents them.

Display rules config: 1

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

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