Performance by cohort

3 year bands · 491,586 tests

Pass rate climbs 16.4 points across the cohorts — newer A4 examples clear the test more reliably than the early cars.

Pre-2018 cohort 440,138

Pass

77.4%

Fail

17.9%

PRS

4.2%

Avg mileage at test

114,621 mi

2018–2020 cohort 50,871

Pass

89.5%

Fail

8.9%

PRS

1.2%

Avg mileage at test

47,677 mi

2021+ cohort 577

Pass

93.8%

Fail

3.8%

PRS

2.1%

Avg mileage at test

26,574 mi

Cohort = vehicle's first-registration year band. Same model, different generations of build.

Generations on file · 4

Audi A4 · UK market

Photos: Wikimedia Commons · CC BY-SA / CC BY / public domain.

The picture

A4 Passes 76.6% — Diesels Carry the Hidden Cost

At an average test mileage of 105,387 — the highest of any car in this analysis — the Audi A4's 76.6% pass rate is reasonable but not exceptional. Worn tyres and fractured springs are the most common failure causes. Dig deeper and diesel running costs mount quickly: EGR failure on a 2015 2.0 TDI ran to £1,500 at 60,000 miles, while an AdBlue module control unit on a 2016 Avant Ultra came in at £930.

Infotainment glitches on newer models are a nuisance rather than a structural problem, but the pattern of diesel-specific component failure is worth factoring into any ownership calculation. A full service history and confirmed EGR and AdBlue system health are non-negotiable checks for any used A4 TDI.

ABI Insurance Group

Group 26–40

Above average — worth comparing quotes before buying. Lower groups cost less to insure; UK fleet average is around Group 22.

Source: ABI Group Rating Panel · administered by Thatcham Research · groups cover standard variants; performance trims may sit higher. Browse all insurance groups →

26–40

out of 50

Compare quotes →

Top ten reasons for rejection.

Filter failures:

Hide wear items to see the model's real defects.

01

Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view

14,447 occurrences · 2.9% of tests
02

A transmission shaft constant velocity joint boot severely deteriorated

13,083 occurrences · 2.7% of tests
03

Tyre tread depth not in accordance with the requirements

12,816 occurrences · 2.6% of tests
04

A spring or spring component fractured or seriously weakened

11,789 occurrences · 2.4% of tests
05

A rear registration plate lamp or light source missing or inoperative in the case of multiple lamps or light sources

11,431 occurrences · 2.3% of tests
06

A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc

10,073 occurrences · 2.0% of tests
07

A suspension pin, bush or joint excessively worn

10,064 occurrences · 2.0% of tests
08

A suspension joint dust cover severely deteriorated

9,182 occurrences · 1.9% of tests
09

A tyre cords visible or damaged

5,873 occurrences · 1.2% of tests
10

a brake lining or pad worn below 1.5mm

5,298 occurrences · 1.1% of tests

Counts cover Major and Dangerous defects logged at test. Advisory items excluded so this shows why a car was rejected, not just what the tester flagged in passing.

Worst-case fix budget · top 3 failures

£148–£370

If every one of this A4's most-logged Major fails hit at the same MOT, that's the real-world UK garage range. Reality is usually one or two items, not all of them. Open the estimator →

Try the calculator

Build your own retest budget.

Year-band analysis

Best year to buy. Worst to avoid.

First-time MOT pass rate split by registration band. A 16.4-point gap between bands means the year you buy Audi A4 has a real effect on what turns up at the garage.

Best band to buy

93.8%

2021+ registration

the 2021-on band climbs to 93.8% — a 16.4-point improvement. Tests in this band average 26,574 miles — roughly 88K miles fewer on the clock than the older band. Failures here are mostly wear items: tread depth below requirements of 1.6mm, damaged but not adversely affecting driver's view — the structural issues that drag down older examples don't appear in the top-10 for this band. Post-2020 examples are early in their MOT life and generally show the cleanest records.

Band to be cautious about

77.4%

Pre-2018 registration

On the older band (pre-2018), the data shows a 77.4% pass rate against a fleet average of 93.8% on the newer band. The main culprits logged at test: damaged but not adversely affecting driver's view, constant velocity boot severely deteriorated, and tread depth below requirements of 1.6mm. Average mileage on test for this band is 114,621 miles — high-mileage wear items are a recurring theme. Honest John records: "Report of vibration from drivetrain of November 2018 Audi A4 B9 avant 272 3.0 V6 now at 45k miles: At 1,250 rpm, whether in D or S mode, there is…"

Best band to buy: 2021+ (93.8% first-time pass). Worst band to avoid: pre-2018 (77.4% pass). That's a 16.4-point spread across 440,138 older tests and 577 newer ones — year of build makes a material difference on this model.

Year-spread leaderboard →

Tools that pre-empt a retest.

Picked against this car's top failure patterns. Affiliate links to Amazon UK — we earn a small cut at no cost to you. Disclosed up-front, doesn't shape the data.

Item 01 · Amazon UK

Digital tyre-tread depth gauge

Five quid for a gauge beats £150 for a retest. UK MOT minimum is 1.6mm — most testers fail anything below 2mm to be safe.

Search Amazon UK

Item 02 · Amazon UK

H7 / W21W bulb pack

A spare-bulb kit lives in the boot. Test morning is not the time to find your stop-lamp's gone.

Search Amazon UK

My Motor World · affiliate

Parts & supplies for this fix

Affiliate links — small commission, no extra cost to you.

Summit

Summit ADRG-215 Audi Replacement Stick-On Tinted Mirror Glass RHS

£9.89

View at My Motor World →

Summit

Summit ADRG-216 Audi Replacement Stick-On Tinted Mirror Glass LHS

£14.29

View at My Motor World →

Draper Expert

Draper Expert Oil Filter Socket for Audi, BMW, Mercedes-Benz, Porsche and VW

£18.69

View at My Motor World →

Draper Expert

Draper Expert Audi/VW Drain Plug Key, 1/2" Sq. Dr.

£21.99

View at My Motor World →

Click Mechanic · affiliate

Book a mobile mechanic

Affiliate links — small commission, no extra cost to you.

Mobile mechanic · UK-wide

Book a mechanic at your door.

Fixed-price quotes upfront. No garage needed. Click Mechanic sends a vetted local mechanic to you — home, work, or roadside.

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Owner reports · Honest John

What owners actually report.

Verbatim faults logged by owners on honestjohn.co.uk over recent years. We didn't summarise — these are the words people typed in.

What's good

Exceptional quality, packed with technology, impressive refinement and comfort, efficient and economical.

Recent owner-reported faults

7 May 2021
Adblue module control unit failure reported on 2016 Audi A4 Avant Ultra 2.0 TDI. Owner quoted £930 to replace the unit.
23 Mar 2020
Owners of three month old car reports problems with the infotainment system. When they get in the car and drive off an error message often comes up saying "The selected user has not been used in this vehicle for a while. Please enter the MyAudi user data again. It will be necessary to switch to the guest user to do this." Local dealer has told the owners that Audi UK are aware of the fault and they are awaiting a software fix from Audi Germany.
20 Dec 2019
Report of failure of EGR on 2015 Audi A4 B9 EA288 2.0TDI at 60,000 miles. Cost of replacement was £1,500.
29 Nov 2019
Report of "persistent vibrations coming through the accelerator pedal and the steering wheel, often simultaneously" in November 2015 Audi A4 B9 avant 8-speed auto, 3.0 TDI V6 272HP. Has had replacement of several expensive parts under guarantee due to factory recalls (4 camshafts, crank shaft, chain tensioner), but problem's remains. In D the vibrations arrive around 1,250 rpm especially when accelerating. Owner notices that despite regular cleaning and quality fuel all the time, the engine is also quite noisy when accelerating: "it's as if there's a part somewhere which is noisier than it should be and injects vibrations into the mix when increasing speed." Also, when the car is hot and in traffic it can start to tremble slightly until shifted into Neutral. If driver leaves car in S in traffic, the vibrations are slightly stronger still.
31 Jul 2019
Owner found that the 19-inch optional alloy wheels fitted to his March 2017 Audi A4 2.0TDI quattro s-tronic s-line had increased its CO2 from 114g/km to 121g/km and put up his annual VED from £30 to £120.
16 Feb 2019
Complaint of "soft knocking sound around driver's right ear" when driving on a "roughish road surface" in a new Audi A4 B9. Seems to be from an area around drivers window/door lock/door pillar. Likely to be the inertia reel seatbelt pendulum.
28 Dec 2018
Report of vibration from drivetrain of November 2018 Audi A4 B9 avant 272 3.0 V6 now at 45k miles: At 1,250 rpm, whether in D or S mode, there is vibration which passes through the accelerator pedal and steering wheel. Also at 1,750 rpm when cruising on the motorway at 80 mph with cruise control on in 8th gear it doesn't feel as smooth as it should. Finally, when around 2,000 rpm the car feels unrefined and actually noisy for an Audi V6 diesel.
7 Aug 2018
Audi dealer told owner that intermittent shudder in 1st gear when releasing the clutch of his 2016 Audi A4 may be due to "driver error" that has damaged the dual mass flywheel and want £1400 to "investigate" (this must include the costs of a new DMF and clutch).
9 Jul 2018
Report of two failed transmissions on 2015 Audi S4 in 25,000 miles. Unfortunately owner failed to renew extended warranty.
15 Jan 2018
Various niggling problems reported with June 2016 Audi A4 B9. In May 2017 the car failed twice, on consecutive days, and the Engine Management Unit was replaced. At the same time owner advised the dealer that the electronic dipstick was reporting the engine oil level as being at full capacity although he had not topped up the oil, that the trip odometer and the long term memory were intermittently clearing to zero and the external thermometer was occasionally displaying obviously faulty temperatures. In July 2017 he again reported to the dealer the potential problems with the electronic dipstick and the other display issues. He was simply told that "new cars don't use oil". The engine oil has not been topped up since first delivery. The trip odometer and long term memory inexplicably reset to zero yesterday.
18 Aug 2017
Report that on 4th August a 7 month old 2017 Audi A4 Avant came to a sudden halt from 38mph for no reason, on a clear road, causing the following car to crash into the back of it.

Source: honestjohn.co.uk · 11 reports indexed

Recall history

32 UK recalls on record.

The A4 has 32 official UK vehicle recalls covering defect details, remedies, and affected build dates.

See all recalls

Buying or keeping an A4?

Use the failure ranking as a pre-test checklist or a haggling lever. Treat the headline pass rate as a fleet-wide trend, not a guarantee on any individual car.

If you own an A4 and your last MOT looked nothing like the ranked failures above, that's normal — individual cars vary widely. The ranking shows the patterns testers flag most often across the country.