Smart fortwo 0.9 Turbo W453

The wastegate actuator on the 0.9 turbo is exposed to water ingress, which corrodes the mechanism over time. When the wastegate sticks open, the car loses boost and feels sluggish. When it sticks closed, the engine overboosts and enters safe mode. Diagnostic codes can be misleading (P0226, P0651, P0335) since none directly point to the wastegate. A wastegate-only repair at a specialist costs around €800-900 including recalibration. Smart officially does not offer a standalone fix and typically recommends a full turbo replacement at €1,500-2,500. This issue is described as "becoming a common problem" on specialist sites like Evilution, particularly after 60,000-80,000 km.

The Getrag 6DCT250 dual-clutch transmission (shared with Renault Twingo and Ford Fiesta/Focus) uses two actuator motors (M14 and M15) to operate the clutch forks. These motors corrode over time, producing a rattling noise and loss of either even gears (reverse, 2nd, 4th, 6th) or odd gears (1st, 3rd, 5th). The lower motor (M15) is a straightforward 5-minute replacement (4 Torx bolts from underneath), costing around €400 including the part. The upper motor (M14) requires removing the intake manifold and is considerably more labor-intensive. Full clutch pack replacement with actuators can reach €1,500-2,000 at a dealer.

The variable valve timing solenoid on the H4B engine is known to stick due to oil contamination and carbon buildup. Symptoms include rough idle (described as the "infamous 453 rough idle problem" in owner communities), check engine light with code P0016, and occasional loss of power. The solenoid can often be cleaned rather than replaced, costing almost nothing for a DIY repair. Professional cleaning or replacement runs €200-350 including labor. Using the correct oil specification (5W-40 A3/B4) and maintaining strict oil change intervals helps prevent this issue.

The F2 fuse box behind the dashboard is prone to contact degradation. Fuse terminals bend and lose proper contact, or tarnish over time. This can cause total power loss to affected systems, intermittent electrical faults, or controller error codes. The issue is identified as "a future common problem" for the 453 by specialist sources. In many cases, cleaning the contacts with electrical contact cleaner and gently compressing the terminals resolves the issue at minimal cost. In more severe cases, terminal replacement is needed. Evilution notes that "the 453 is just a Renault, so you should expect Renault electrical quality."

A known quirk of the W453 is electric windows sticking in the down position. The windows can usually be closed by incrementally nudging them up with short switch activations, but this indicates a failing window motor or regulator. Water damage to the window control module has been reported as a contributing factor. Replacement of the window regulator motor runs €200-500 depending on whether OEM or aftermarket parts are used.

The supply and return oil pipes feeding the turbo can develop leaks due to corrosion, particularly the coolant pipe adjacent to the turbo oil lines. Symptoms include oil drips under the car when parked and oil spots on the rear bodywork when driven. If caught early, replacing the pipes costs €300-500. If the turbo oil-starves due to a restricted feed pipe, the Garrett floating bearing turbo can fail, escalating the repair to a full turbo replacement at €1,500-2,500.