Model Reports 4 min read Updated 18 Oct 2026

Porsche 911 2005: reliability & common MOT faults

In 2025, 86 in every 100 first MOTs on a 2005 Porsche 911 were passes. Most common reason for a fail: Petrol emissions (with catalyst).

Summary

The 2005 Porsche 911 follows the pattern of the model years either side.

At a glance

How 2,641 first tests went in 2025.

Passed first time
86 in every 100
Did not pass first time
14 in every 100370 failed first-attempt tests
The typical car
20 yearsabout 71,534 miles
First tests counted
2,641

What failed most often

  1. Petrol emissions (with catalyst)21 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 2005 Porsche 911 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.

Noise, emissions and leaks

One fault: petrol emissions (with catalyst), 3.9 times as often as on similar cars.

Figures below are measured across the 369 of 370 failed first attempts (99.7%) that recorded an odometer reading in 2025. Mileage is needed to compare like with like.

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.

Petrol emissions (with catalyst)

Failed on 76 first tests3.9 times as often as similar carsLikely evidence

What it means

Emissions levels over the manufacturer's specified limits are Major, as are levels over default limits, which apply when no exact match is found for the vehicle. Dense blue or clearly visible black smoke at idle, held for a set period, is Major, except for certain older vehicles and two stroke engines where smoke is unavoidable. An induction or exhaust leak that could affect emissions levels is Major too.

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

Brakes

One fault: rigid brake pipes (front), 2.9 times as often as on similar cars.

Rigid brake pipes (front)

Failed on 22 first tests2.9 times as often as similar carsPossible evidence

What it means

Chafing, corrosion or damage to a rigid brake pipe justifies rejection once its wall thickness is reduced by a set amount, although DVSA accepts this is not easy to determine. If a tester is not sure, the benefit of the doubt applies. A leaking pipe or connection is graded Dangerous on a hydraulic system and Major on an air system.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 56 first tests, 2.5 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
86in 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
12in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 86.0% of 2,641 first tests (2025): only cars that passed first time count. Official-style pass 88.3%: cars fixed at the test station also count as a pass. The 2 fixed and the 12 not fixed make the 14 in every 100 that did not pass first time.

Same model, other years

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

406080100199520002005201020152020Older carsNewer cars
4060801002000200520102020Older carsNewer 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, 84 in every 100 passed first time.

YearPassed first timeFirst tests
199489 in every 100483
199588 in every 100609
199689 in every 100911
199788 in every 100685
199882 in every 100912
199980 in every 1001,106
200081 in every 100867
200183 in every 1001,408
200280 in every 1002,221
200381 in every 1002,429
200484 in every 1002,303
2005 This car86 in every 1002,641
200687 in every 1002,586
200787 in every 1002,331
200889 in every 1001,754
200990 in every 1001,400
201090 in every 1001,662
201191 in every 1001,247
201293 in every 1001,477
201395 in every 1001,211
201493 in every 1001,479
201595 in every 1001,654
201694 in every 1001,620
201794 in every 1001,786
201894 in every 1002,034
201995 in every 1002,183
202096 in every 1001,429
202197 in every 1001,611
202295 in every 1002,460

If you are buying one

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

Mileage matters most on a 2005 Porsche 911.

Of 2005 Porsche 911 vehicles with under 48,000 miles, 92 in every 100 passed their 2025 MOT first time. With 94,000 miles or more, 81 in every 100 did.

Under 48,000527 tests
92
48,000–64,000527 tests
90
64,000–78,000 Typical car534 tests
85
78,000–94,000517 tests
82
94,000 and over535 tests
81

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 48,00064,000–78,00094,000 and over
Petrol emissions (with catalyst)0.93.24.1

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

When a car fails

45in every 100

of failed cars had one item to fix.

28in every 100

of failed cars had three or more items to fix.

2in 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.

The 2005 Porsche 911 follows the pattern of the model years either side. Its main cause of failure was Petrol emissions (with catalyst), about 21 in every 100 failed tests. In 2025, 86.0% of 2,641 first MOTs on the 2005 Porsche 911 passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 88.3%. Among 370 failed first-attempt MOT tests (test year 2025), Petrol emissions (with catalyst) appears more often than on similar cars (20.6% of those tests; 76 observed failures; about 3.9× 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 2005 Porsche 911 at the first attempt were Petrol emissions (with catalyst) (20.6%), 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: Petrol emissions (with catalyst) (20.6% of those tests; 76 observed failures; about 3.9× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Petrol emissions (with catalyst) shows up more often than on similar cars (20.6% of those tests; 76 observed failures; about 3.9× 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 2005 Porsche 911 include Petrol emissions (with catalyst), Rigid brake pipes (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 2005 Porsche 911 (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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