Fault File
All models / All cars / City cars / SEAT Mii

SEAT Mii

All generations and engines together · 18,638 MOT tests in the 2025 data · typical mileage at age 7: 42k

First-time failure at age 7
18.7%
Across 1,332 tests. The average across all tracked models is 19.5%.
Rank at age 7
129 of 239
1 = lowest failure rate among the models tracked.
Typical mileage at age 7
42k miles
Check the mileage view below; low-mileage models can look better by age than they are.

How this model wears

SEAT MiiClass average, all tracked models

Known issues

Measured

Computed from DVSA MOT results, all of Great Britain, 2025. Nothing here is opinion.

What testers flag

Share of tests where each item was recorded. The dark tick is the class average across all tracked models; bars are scaled within each group.

Faults with the car itself

The rows that judge the model rather than its keeper. 6,847 tests in this band.

A suspension pin, bush or joint excessively worn
Advisory
10.4%class 5.9%
A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning
Fail
4.0%class 1.3%
A suspension pin, bush or joint excessively worn
Fail
2.9%class 0.9%
Significant brake effort recorded with no brake applied indicating a binding brake
Advisory
2.5%class 0.7%
Significant brake effort recorded with no brake applied indicating a binding brake
Fail
1.6%class 0.2%
Fuel system leaking, or missing or ineffective filler cap
Fail
1.6%class 0.0%
Lambda coefficient outside the default limits or the range specified by the manufacturer
Fail
1.6%class 0.2%
Play in steering rack inner joint(s)
Advisory
1.5%class 1.1%
Brake pipe damaged or excessively corroded
Advisory
1.5%class 1.9%
Excessive fluctuation in brake effort through each wheel revolution.
Advisory
1.2%class 0.6%

Wear, upkeep and luck

Tyres, pads and stone chips say more about how the car was driven and maintained than about how it was built.

A tyre seriously damaged
Advisory
23.6%class 11.1%
Tyre tread depth not in accordance with the requirements
Advisory
19.1%class 22.9%
Brake disc or drum excessively weakened, insecure or fractured
Advisory
7.7%class 10.1%
A brake lining or pad worn below 1.5mm
Advisory
5.1%class 8.7%
Brake disc or drum significantly and obviously worn
Advisory
3.8%class 3.4%
The aim of a headlamp is not within limits laid down in the requirements
Fail
3.1%class 2.1%
Wiper blade missing or obviously not clearing the windscreen
Fail
2.3%class 1.7%
Tyre tread depth not in accordance with the requirements
Fail
2.0%class 2.2%

Unconfirmed issues

Reported

Owner folklore from forums and the motoring press. Most of it never shows up in an MOT, which is why this section exists at all.

Notchy gearchanges and gearbox crunching

Emerging

A recurring owner complaint on the 5-speed manual: crunching or resistance selecting first and reverse, especially after the car has sat for a while, which owners put down to synchromesh wear. It comes up repeatedly across the shared VW Up/SEAT Mii/Skoda Citigo platform, and dealers aren't always quick to acknowledge it as anything other than normal. Reported from fairly low mileage on some cars, and a synchro or full gearbox rebuild runs into four figures if it's left to get worse.

Reported from low mileage upward · sources: SEATCUPRA.net forum, Honest John owner review, BriSkoda forum

Suspension knocks and a crashy ride

Partly in the MOT data

Owners report knocking from the suspension and a ride that turns crashy and unsettled over potholes and speed bumps, sometimes noticed within the first few thousand miles. The measured data backs this up: suspension is the standout MOT fault for this car's segment, so the noise owners describe does line up with real wear showing at test time, not just an irritating rattle that goes nowhere.

Reported from low mileage · sources: SEATCUPRA.net forum (owner report and separate moderator test drive)

Airbag welding defect and child lock recalls

Confirmed pattern

Two official recalls affect narrow production windows: cars built 12-15 June 2013 may have airbag control units with incorrect welding that can stop the driver's airbag deploying properly, and cars built 25 November 2015 to 14 April 2016 have a child lock that can disengage on its own, letting rear doors be opened from inside. Both were formally recalled and the fix should already be logged against the VIN if it's been done, so no cost to a buyer if it's still outstanding. Two further towing-eye welding recalls cover 2015-2017 build cars, a minor fix affecting the tool kit rather than the car itself.

Narrow build-date windows only · sources: car-recalls.co.uk (DVSA recall data), Auto Insider, What Car

Small 12V battery failure

Electric only

On the Mii Electric, the low-voltage 12V battery under the bonnet that wakes the car up and runs the electronics is a repeatedly reported weak point. Symptoms are a car that won't wake up to charge, dim or flickering interior lights, or a sluggish start. It's a cheap part to replace but a confusing one to diagnose if you don't know to check it first, since it's separate from the main traction battery. Doesn't apply to the petrol Mii.

Reported across ownership ages · sources: SpeakEV forum, Up Owners Club forum, MyCarly owner reports

Cambelt interval on the 1.0 MPI is genuinely unclear

Disputed

The non-turbo 1.0-litre three-cylinder petrol uses a timing belt, not a chain, and VW Group's own guidance on when to change it has shifted over the years: from 5 years/60-80k miles on early cars to talk of 120k-mile inspection-only or effectively lifetime belts more recently. Independent mechanics stay cautious and often recommend changing it well before trusting a 'lifetime' claim, since this is an interference engine and a snapped belt wrecks the pistons and valves. Budget roughly £300-500 if there's no paperwork proving it's been done.

1.0 MPI petrol only, not the TSI or electric · sources: Honest John owner review, Up Owners Club forum, pmmonline.co.uk

Viewing one? Ask this

Built from the two sections above.

Select first and reverse gear from cold, straight after starting. Crunching or resistance is the synchro-wear complaint owners report on the manual box.
Drive over a rough patch or speed bumps at low speed and listen. Knocks from the suspension match the pattern behind this car's measured MOT suspension failures.
Check the V5C build date against the DVSA recall checker before buying. Cars built June 2013 or Nov 2015 to Apr 2016 need the airbag or child-lock recall work confirmed done.
On a Mii Electric, check it wakes up and charges without needing the ignition cycled first. A car that won't wake from cold or has flickering lights points to the known 12V battery fault.
Ask for cambelt history and a receipt on a 1.0 MPI petrol, not just 'it's a lifetime belt'. No paperwork means budget for one anyway rather than trust the latest interval guidance.
Take a longer test drive through several full-warmth gear changes, not just round the block. Crunching that persists once the car is warm, not just cold, points to a synchro problem that needs sorting.
Check the fuel gauge reading against a known fill-up over a longer drive. Owners report gauges reading emptier than reality, a known but harmless annoyance worth knowing about upfront.

Others in its class

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