At a Glance
The Smart Forfour has 9 identified common problems across 2 generations, with the Mk1 (2004-2006) being the most affected generation and tyres & wheels the most common problem category. Based on 234K MOT tests from DVSA data.
Problems are patterns in the DVSA data that occur significantly more often on a specific model than the UK average — confirmed at 99% statistical confidence. Read our DVSA MOT data methodology →
Below: generation-by-generation comparison of Smart Forfour common problems, MOT failure types, and pass-rate data drawn from DVSA records. Click any generation to see fuel- and engine-specific fault patterns, mileage-banded repair guidance, and the most common MOT failures testers record.
MOT Tests & Failures by Generation
Smart Forfour generations by MOT tests, failures, and identified problems from DVSA data
Hover over each bar for a full breakdown. Tap any bar to view that generation's problems.
Showing total MOT tests, failures, and known problems per make. Hover over each bar for a full breakdown.
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Browse Smart Forfour Generations
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Most Common Smart Forfour MOT Failures
Every reason Smart Forfour vehicles fail their MOT, ranked by frequency. Select an individual year to see only that year’s failures, or stay on ‘All time’ for the combined picture across our 20 years of DVSA data. Scroll inside the table for the full list.
| # | Failure | % of failures |
|---|---|---|
| 1 | Wiper blades deteriorated | 10.02% |
| 2 | Number plate lamp not working | 9.33% |
| 3 | Tyre tread depth below limit | 8.51% |
| 4 | Tyre condition | 8.36% |
| 5 | Stop lamp not working | 6.16% |
| 6 | Brake pads or linings worn | 5.44% |
| 7 | Suspension joint or bush worn | 5.15% |
| 8 | Windscreen washer not working | 4.25% |
| 9 | Brake performance below minimum | 3.80% |
| 10 | Headlamp fault | 3.15% |
| 11 | Front lamp not working | 2.78% |
| 12 | Headlamp aim defect | 2.43% |
| 13 | Brake disc or drum worn | 2.29% |
| 14 | Coil spring broken or corroded | 2.22% |
| 15 | Indicator fault | 2.10% |
| 16 | Position lamp not working | 1.91% |
| 17 | Spark ignition emissions above threshold | 1.89% |
| 18 | Parking brake performance below minimum | 1.83% |
| 19 | Track rod end worn | 1.81% |
| 20 | Ball joint dust cover split | 1.78% |
| 21 | Exhaust system fault | 1.36% |
| 22 | Driveshaft fault | 1.01% |
| 23 | Windscreen damage affecting view | 0.92% |
| 24 | Shock absorber worn or leaking | 0.82% |
| 25 | Rear suspension fault | 0.76% |
| 26 | Battery loose or leaking | 0.67% |
| 27 | Mirror damaged or missing | 0.67% |
| 28 | Wheel bearing worn | 0.63% |
| 29 | Airbag warning light on | 0.61% |
| 30 | Catalytic converter efficiency low | 0.56% |
| 31 | Parking brake condition | 0.41% |
| 32 | Horn not working | 0.39% |
| 33 | ABS fault | 0.38% |
| 34 | Fog lamp not working | 0.35% |
| 35 | Tyre size or type not matched | 0.35% |
| 36 | Seat belt condition | 0.32% |
| 37 | Front suspension fault | 0.28% |
| 38 | Brake lever fault | 0.27% |
| 39 | Rear lamp not working | 0.24% |
| 40 | Compression ignition emissions above threshold | 0.24% |
| 41 | Brake caliper fault | 0.22% |
| 42 | Flexible brake hose damaged | 0.18% |
| 43 | Rear fog lamp not working | 0.17% |
| 44 | Rear reflector damaged or missing | 0.17% |
| 45 | Brake hydraulic component worn | 0.15% |
| 46 | Body corrosion or damage | 0.14% |
| 47 | Front passenger door fault | 0.14% |
| 48 | Handbrake lever fault | 0.13% |
| 49 | Tyre valve stem damaged | 0.13% |
| 50 | Fuel cap damaged or missing | 0.11% |
| 51 | Brake pedal movement restricted | 0.10% |
| 52 | Bumper damaged or insecure | 0.09% |
| 53 | Brake pedal fault | 0.09% |
| 54 | Front suspension joint worn | 0.09% |
| 55 | Steering rack fault | 0.09% |
| 56 | Suspension linkage fault | 0.08% |
| 57 | Electronic stability control fault | 0.08% |
| 58 | Brake cable, rod, lever or linkage fault | 0.07% |
| 59 | Undertray damaged or missing | 0.06% |
| 60 | Electrical switch fault | 0.06% |
| 61 | Rigid brake pipe corroded or damaged | 0.06% |
| 62 | Suspension arm worn or corroded | 0.06% |
| 63 | Engine oil leak | 0.06% |
| 64 | Brake fluid level low or contaminated | 0.05% |
| 65 | Driver door fault | 0.05% |
| 66 | Tyre pressure monitoring system fault | 0.05% |
| 67 | Headlamp levelling device fault | 0.05% |
| 68 | King pin or swivel pin worn | 0.05% |
| 69 | Brake fluid leak | 0.04% |
| 70 | Steering operation fault | 0.04% |
| 71 | Chassis condition | 0.03% |
| 72 | Driver airbag fault | 0.03% |
| 73 | MacPherson strut worn | 0.03% |
| 74 | Electric power steering fault | 0.03% |
| 75 | Handbrake cable fault | 0.03% |
| 76 | Propshaft fault | 0.02% |
| 77 | Hydraulic brake cylinder fault | 0.02% |
| 78 | Vehicle structure corrosion | 0.02% |
| 79 | Bonnet catch or hinge fault | 0.02% |
| 80 | Electrical wiring fault | 0.02% |
| 81 | Boot lid damaged or insecure | 0.02% |
| 82 | Dashboard warning lamp fault | 0.02% |
| 83 | Brake fluid warning light on | 0.02% |
| 84 | Reversing lamp not working | 0.02% |
| 85 | Anti-roll bar worn or corroded | 0.02% |
| 86 | Mirror or camera fault | 0.02% |
| 87 | Body security fault | 0.02% |
| 88 | Fuel tank corroded or leaking | 0.02% |
| 89 | Brake fluid reservoir fault | 0.01% |
| 90 | Engine mounting worn or broken | 0.01% |
| 91 | Transmission drive belt fault | 0.01% |
| 92 | Steering lock fault | 0.01% |
| 93 | Suspension mounting corroded | 0.01% |
| 94 | Suspension unit fault | 0.01% |
| 95 | Fuel pipe corroded or damaged | 0.01% |
| 96 | Passenger seat fault | 0.01% |
| 97 | Rear fog lamp warning light fault | 0.01% |
| 98 | Steering arm worn | <0.01% |
| 99 | Window damaged or won't operate | <0.01% |
| 100 | Main beam warning light fault | <0.01% |
| 101 | Driver seat fault | <0.01% |
| 102 | Speedometer fault | <0.01% |
| 103 | Drag link end worn | <0.01% |
| 104 | Electronic braking system fault | <0.01% |
| 105 | Daytime running lamp not working | <0.01% |
| 106 | Dip switch fault | <0.01% |
| 107 | Exhaust leak | <0.01% |
| 108 | Fuel hose damaged or leaking | <0.01% |
| 109 | Subframe corrosion or damage | <0.01% |
| 110 | Transmission oil leak | <0.01% |
| 111 | Front fog lamp not working | <0.01% |
| 112 | Passenger airbag fault | <0.01% |
| 113 | Steering drive system fault | <0.01% |
| 114 | Steering free play excessive | <0.01% |
| 115 | Steering column fault | <0.01% |
| 116 | Brake air or vacuum system fault | <0.01% |
| 117 | Brake master cylinder fault | <0.01% |
| 118 | Tailgate damaged or insecure | <0.01% |
| 119 | Brake servo fault | <0.01% |
| 120 | Brake valve fault | <0.01% |
| 121 | Hazard warning light fault | <0.01% |
| 122 | Indicator warning light fault | <0.01% |
| 123 | Seat belt or padding damaged | <0.01% |
| 124 | Spring mounting corroded | <0.01% |
| 125 | Steering wheel damaged or insecure | <0.01% |
| 126 | Suspension linkage attachment bracket or mounting corroded | <0.01% |
| 127 | Towbar fault | <0.01% |
| 128 | Axle corroded or damaged | <0.01% |
| 129 | Brake back plate corroded or damaged | <0.01% |
| 130 | Brake pressure or vacuum buildup insufficient | <0.01% |
| 131 | Brake relay lever fault | <0.01% |
| 132 | Reversing lamp switch fault | <0.01% |
| 133 | Seat belt anchorage fault | <0.01% |
| 134 | Vehicle floor corroded | <0.01% |
| 135 | Steering coupling worn | <0.01% |
| 136 | Axle beam corroded or cracked | <0.01% |
| 137 | Body strengthening plate corroded | <0.01% |
| 138 | Brake clevis joint worn | <0.01% |
| 139 | Brake wheel cylinder fault | <0.01% |
| 140 | Exhaust emissions above threshold (non-catalyst) | <0.01% |
| 141 | Exhaust heat shield or sound insulation damaged | <0.01% |
| 142 | Full power hydraulic brake fault | <0.01% |
| 143 | Hydraulic fluid leak | <0.01% |
| 144 | Leaf spring broken or corroded | <0.01% |
| 145 | Loading door damaged or insecure | <0.01% |
| 146 | Outline marker lamp not working | <0.01% |
| 147 | Passenger compartment corrosion | <0.01% |
| 148 | Passenger hand grip fault | <0.01% |
| 149 | Power steering pipe or hose leaking | <0.01% |
| 150 | Power steering pump fault | <0.01% |
| 151 | Seat belt pre-tensioner fault | <0.01% |
| 152 | Steering intermediate drop arm worn | <0.01% |
| 153 | Subframe mounting corroded | <0.01% |
| 154 | Suspension rod worn or corroded | <0.01% |
| 155 | Torsion bar worn or corroded | <0.01% |
| 156 | Universal joint worn | <0.01% |
Showing all 156 reasons — scroll inside the table for the full list.
Smart Forfour MOT Failures by Category
Total MOT failure occurrences for the Smart Forfour, grouped by category. Same data as the failures table above — just sliced by category instead of fault title. Hover a slice for the top failures in each category.
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Frequently Asked Questions
What are the most common Smart Forfour problems?
Based on analysis of 234K Smart Forfour MOT tests from DVSA data, we have 9 identified common problems across 2 generations. The most frequently flagged issue is "Wiper blades deteriorated". Tyres & Wheels is the most common problem category.
Which Smart Forfour generation has the most problems?
The Smart Forfour Mk1 (2004-2006) (2004–2006) has the highest number of identified common problems (7). Click the generation card above for the full breakdown.
How is this data calculated?
We analyse anonymised DVSA MOT test records under the Open Government Licence. An issue is classified as a "Common Problem" when it occurs significantly more often on a specific model than the UK average, confirmed at 99% statistical confidence. Read the full methodology page for details.
Can I report a problem with my Smart Forfour?
Yes — use the "Tell Us About Your Problem" form on this page. Your report helps other Smart Forfour owners spot problems early. All submissions are reviewed before being added to the public database.
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