Smart ForTwo 451
Weaknesses, engine ratings and buying advice
98 PS
ForTwo · Benzin
Brabus kart
Fun to Drive!41–54 PS
0.8L CDI Diesel
4 weaknesses
Stay Away!Body Variants
The Smart ForTwo 451 is available as Coupé and Convertible — choose your body type for specific insurance data:
Generations
Engine Overview
The Smart ForTwo 451 is available with 4 engine variants — from 41 to 102 hp.
The smallest production diesel of its time. Fundamentally unsuited to city driving and short trips — precisely the use case of most Smart owners. DPF problems, turbo wear and high repair costs relative to vehicle value make the CDI an engine to avoid. The petrol engines are the far better choice.
- !! Turbocharger damage from icing in the intake tract from 60,000 km
On Euro 5 models (54 hp) a sensor was incorrectly positioned. In winter, ice can form in the intake tract and damage the turbocharger. Limp mode activates.
Symptoms: Engine limp mode in winter, power loss, whistling noises from the turbocharger, engine warning light - !! Injectors coked up or faulty from 130,000 km
The injectors of the OM660 coke up through frequent short-trip use. At 150,000 km and beyond, cold-start problems and rough running appear.
Symptoms: Poor cold start, rough running, power loss, increased consumption, heavy smoke - !! Diesel particulate filter clogged from 80,000 km
The DPF on the Smart CDI clogs frequently because the vehicle is typically used for short trips. Regeneration requires 20–30 minutes of sustained driving at around 120 km/h.
Symptoms: Power loss, DPF warning light, increased consumption, engine enters limp mode, regeneration does not complete
+ 1 more engine weaknesses + vehicle weaknesses
The Mitsubishi three-cylinder in the ForTwo 451 is fundamentally a solid engine. In naturally aspirated form it is very frugal and dependable; the turbo version offers noticeably more driving fun at a slightly higher maintenance requirement.
- !! Timing chain tensioner and guide wear from 90,000 km
The timing chain tensioner guide consists of two parts — the yellow sliding coating dissolves, causing a loose timing chain and in the worst case valve damage. Mainly affects engines with neglected oil changes.
Symptoms: Rattling on cold start (disappears after about 1 second), engine warning light, sudden power loss - !! Clutch actuator wears out — electric motor shaft shears off from 100,000 km
The shaft of the electric motor in the clutch actuator breaks from around 100,000 km. The Softtouch gearbox shifts with jerks or not at all. Display shows only 3 bars, no gear can be selected.
Symptoms: Jerky gear changes, transmission limp mode, '3 bars' shown on display, no gear selectable, fault codes P0120/P0222/P0123 - !! Ignition coil failure — misfires on individual cylinders from 60,000 km
Faulty ignition coils cause misfires on individual cylinders. With a 3-cylinder engine even one failure is very noticeable. Cylinders 2 and 3 are most frequently affected.
Symptoms: Engine warning light, pronounced jerking, power loss, rough idle, misfires on individual cylinders
+ 6 more engine weaknesses + vehicle weaknesses
Electric variants of the ForTwo and ForFour. Various battery sizes depending on generation and facelift.
No known weaknesses documented.
Electric variants of the ForTwo and ForFour. Various battery sizes depending on generation and facelift.
No known weaknesses documented.
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| Clutch Actuator Defective (3-Bar Fault) The electric clutch actuator (part no. A4512500062) frequently fails from 80,000–100,000 km. The shaft of the internal electric motor breaks, and gears can no longer be selected. Three dashes on the display, limp mode, or vehicle completely undriveable. Symptoms: Three dashes/bars on display instead of gear readout, gearbox does not clutch or judders heavily, vehicle in limp mode from 90,000 km | Medium | |
| Gearbox Shift Actuator Defective The shift actuator (part no. A4518290201) controls the electronic gear selection. When it fails, individual gears are lost or the gearbox no longer shifts at all. Typical problem on older examples from 100,000 km. Symptoms: Individual gears cannot be engaged, shifting problems, limp mode, error message on display from 100,000 km | Medium |
Test Reports
TÜV Report 2023
Smart ForTwo 451 shows average defect rates. Notable for lighting (headlight alignment) and exhaust system (corrosion). Suspension and brakes within the average.
2023-01ADAC Pannenstatistik 2023
Smart ForTwo 451 stands out in breakdown frequency due to ignition system problems and gearbox actuator failures. Battery issues also more frequent than comparable vehicles.
2023-06AUTO BILD TÜV-Report 2025
At the MOT the ForTwo 451 puts its successor in the shade. Suspension components even come in below the class average for defects. Driveshafts remain consistently trouble-free. Brake lines are considered the main weak point.
2024-11Top Reported Issues
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Known Problems and Issues +
A total of 27 weaknesses have been documented for the Smart ForTwo 451 (2007–2014) — 13 engine-related and 14 vehicle-related. One problem engine: OM660 (0.8L CDI). Typical issues affect Gearbox, Rust, Electronics, Steering.
ForTwo (OM660, 2007–2014) — Stay Away!: Turbocharger damage from icing in the intake tract, Injectors coked up or faulty, Diesel particulate filter clogged. Power: 41–45 PS.
ForTwo (OM660, 2009–2014) — Stay Away!: Turbocharger damage from icing in the intake tract, Injectors coked up or faulty, Diesel particulate filter clogged. Power: 54 PS.
ForTwo (3B21, 2007–2014) — Be Careful: Timing chain tensioner and guide wear, Clutch actuator wears out — electric motor shaft shears off, Ignition coil failure — misfires on individual cylinders. Power: 61 PS.
ForTwo (3B21, 2007–2014) — Be Careful: Timing chain tensioner and guide wear, Clutch actuator wears out — electric motor shaft shears off, Ignition coil failure — misfires on individual cylinders. Power: 71 PS.
ForTwo (3B21, 2007–2014) — Be Careful: Timing chain tensioner and guide wear, Clutch actuator wears out — electric motor shaft shears off, Ignition coil failure — misfires on individual cylinders. Power: 84 PS.
ForTwo (3B21, 2007–2014) — Be Careful: Timing chain tensioner and guide wear, Clutch actuator wears out — electric motor shaft shears off, Ignition coil failure — misfires on individual cylinders. Power: 98–102 PS.
What to watch out for with the Smart ForTwo? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
What problems and weaknesses does the Smart ForTwo 451 have? +
What should I look for when buying a used Smart ForTwo 451? +
Which engine is recommended? +
Which Smart ForTwo 451 engine is the most fun? +
Is the Smart ForTwo 451 worth buying used? +
What horsepower variants are available for the Smart ForTwo 451? +
Last updated: February 2026 · All information without guarantee