Smart (mcc) Forfour MOT Failures

An analysis of 198,426 real DVSA MOT tests on the Smart (mcc) Forfour — what fails, how often, and how that compares to every other car on UK roads. Generations covered: W454 (2004–2006), W453 (2014–2019).

Where the Smart (mcc) Forfour fails its MOT

The single biggest MOT failure point on the Smart (mcc) Forfour is stop lamp with a multiple light source up to 1/... — this model is 55 times more likely to fail on this item than the average car on UK roads. That makes it a major concern for anyone buying or owning this model. Across 198,426 MOT tests, 5.63% of all Smart (mcc) Forfour tests recorded this as a failure.

Lighting faults are usually straightforward to fix (bulbs, connectors, earth points) but can indicate deeper wiring issues on older cars. Check all lights including fog lamps, number plate lights, and dashboard warning lights.

Other notable weak points include emissions failure (21x the fleet average), headlight fault (19x the fleet average), wheel badly distorted or wear between wheel and... (16x the fleet average), and bumper insecure or with damage (11x the fleet average). These ratios compare the Smart (mcc) Forfour's failure rate on each item against the national average for all cars tested — a ratio of 10x means this model fails ten times more often than a typical car.

The failures span 5 categories: Lights & Electrics, Exhaust & Emissions, Wheels, Bodywork, Suspension. If you're inspecting a Smart (mcc) Forfour before purchase, these are the areas to focus on — and if any have been flagged as advisories on a previous MOT, they're likely to become failures in the near future.

How failures change with mileage

The Smart (mcc) Forfour's weak points shift as the car covers more miles. Understanding these patterns helps you know what to expect — and what to budget for — at each stage of ownership.

Under 60,000 miles

At this mileage, most failures are either design-related or caused by age rather than wear. Components like bushes and drop links may not have been replaced yet, and original-fit parts can deteriorate even on low-mileage cars that spend a lot of time sitting.

For the Smart (mcc) Forfour specifically, the DVSA data shows the most common failures at this mileage are stop lamp with a multiple light source up to 1/... (55x the average) and headlight fault (19x). brake hoses perished or damaged (13x) and anti-roll bar links worn (9.9x) also appear frequently.

60,000 to 100,000 miles

This is where routine wear items start to show up. Brake components, tyres, and exhaust parts have done serious work by this point. Cars that have been well serviced will show fewer of these failures — this mileage band is where good maintenance really separates the well-kept from the neglected.

For the Smart (mcc) Forfour specifically, the DVSA data shows the most common failures at this mileage are body panel damage (95x the average) and stop lamp with a multiple light source up to 1/... (22x). headlight fault (19x) and any part of the noise suppression system insecure (16x) also appear frequently.

Over 100,000 miles

High-mileage cars accumulate failures across multiple systems. The key question isn't whether things will need doing — they will — but whether the car has been maintained well enough to keep on top of them. Look for a consistent service history and recent MOT passes with minimal advisories.

For the Smart (mcc) Forfour specifically, the DVSA data shows the most common failures at this mileage are body panel damage (92x the average) and stop lamp with a multiple light source up to 1/... (26x). headlight fault (17x) and track rod ends worn (11x) also appear frequently.

The shift from stop lamp with a multiple light source up to 1/... at lower mileages to body panel damage at higher mileages is typical — early failures tend to be design or factory-related, while high-mileage failures reflect accumulated mechanical wear. A car that's been well maintained will usually dodge the worst of both.

Known issues beyond the MOT

An MOT only tests roadworthiness at a single point in time — it won't catch developing faults, intermittent problems, or issues that haven't yet reached the failure threshold. These are the issues that Smart (mcc) Forfour specialists and owners flag most frequently, drawn from manufacturer technical bulletins, workshop data, and verified owner reports.

Emissions system failure (W453) Major

The 0.9L turbocharged and 1.0L naturally aspirated engines in W453 ForFour show exceptionally high MOT failure rates for emissions-related defects. Affects W453; typical independent garage repair cost is £200–£600.

Suspension joint wear (W454) Major

First-generation ForFour models show MOT failure rates nearly 10 times the fleet average for suspension component wear, particularly affecting ball joint dust covers and suspension bushes. Affects W454; typical independent garage repair cost is £300–£600.

Wheel bearing failure (W454) Major

MOT data shows first-generation ForFour models fail for wheel bearing roughness at over 12 times the fleet average. Affects W454; typical independent garage repair cost is £150–£300.

Steering rack gaiter deterioration (W454)

MOT data shows W454 ForFour models fail at nearly 13 times the fleet average for steering rack gaiter and ball joint dust cover deterioration. Affects W454; typical independent garage repair cost is £80–£150.

For the complete picture — including repair costs across independent, specialist, and dealer garages — see the full Smart (mcc) Forfour common problems breakdown.

What to check before buying a Smart (mcc) Forfour

Based on the MOT failure data and known issues above, here's what to prioritise when inspecting a Smart (mcc) Forfour:

Lights & Electrics — check for stop lamp with a multiple light source up to 1/..., headlight fault. Exhaust & Emissions — check for emissions failure, any part of the noise suppression system insecure. Wheels — check for wheel badly distorted or wear between wheel and....

Beyond the MOT items, ask specifically about emissions system failure and suspension joint wear. These won't show up on a standard MOT but can be expensive to fix — repairs start from £200. A specialist pre-purchase inspection is worth the investment on this model.

Always check the car's full MOT history for patterns — recurring advisories often become failures within 12 months. And verify the service history to confirm maintenance has been kept up to schedule. Enter any reg into our free car check to see the complete picture.

MOT failure data sourced from DVSA bulk test records via data.gov.uk. Ratios compare this model's failure rate against the national fleet average. Known issues sourced from manufacturer bulletins, specialist workshops, and verified owner reports.