IsItAGoodCar
Reliability Guide

Common Problems with the
2005 Smart Fortwo (450)

By 2005 the 450 Fortwo had been updated with the 700cc engine and the SAM unit was fitted from 2003 onwards. These mid-life cars represent the best balance of value and reliability in the 450 range, though the gearbox and water ingress issues remain. The Roadster (452) was also available during this period.

What changed for 2005

  • •700cc engine replaced the 600cc from 2003
  • •SAM unit fitted from 2003 — vulnerable to water damage
  • •Roadster (452) available from 2003–2005
  • •Improved interior quality over earlier cars

Common MOT watch-outs

  • !SAM unit water damage from door seals and wiper tray
  • !Three bars of death gearbox fault
  • !Engine longevity concerns at higher mileages
  • !Cracked ABS reluctor rings
4
Known Issues
3
Serious
1
Moderate
0
Minor

All Known Issues

Engine Longevity and Oil Consumption

SeriousEngine

The 600cc (pre-2003) and 700cc (post-2003) engines have a limited lifespan. Piston rings wear prematurely, leading to oil burning, fouled plugs, and burnt valves.

Est. Repair Cost: £800–£1,800
Warning Signs:

Blue smoke on acceleration, Misfiring under load, High oil consumption (more than 1L per 1000 miles)

What to Inspect:
  • Check for smoke after the car has idled for 5 minutes
  • Look for oily residue in the TIK pipe (turbo inlet)
  • Ask for compression test results if possible
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SAM Unit Water Damage

SeriousElectrics & Electronics

Water leaks through the windscreen seals or door mirrors and drips directly into the SAM (Signal Acquisition and Management) unit, which acts as the main fuse box and ECU controller.

Est. Repair Cost: £400–£900
Warning Signs:

Wipers staying on, Headlights flickering, Car refusing to start, Central locking behaving erratically

What to Inspect:
  • Check for damp carpets under the dashboard
  • Look for green corrosion on the SAM unit connectors
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Three Bars of Death (Gearbox Fault)

SeriousGearbox & Transmission

A generic error on the dash indicating the gearbox cannot find a gear. Usually caused by a failed actuator, chafed wiring harness, or a worn clutch.

Est. Repair Cost: £200–£700
Warning Signs:

Three horizontal bars on the gear display, Car stuck in neutral, Harsh "clunking" when trying to select gear

What to Inspect:
  • Inspect the wiring harness leading to the gearbox for chafing
  • Check the clutch actuator for free movement
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Cracked ABS Reluctor Rings

ModerateBrakes

The metal rings on the rear driveshafts rust, expand, and snap. This confuses the ABS system.

Est. Repair Cost: £100–£250
Warning Signs:

ABS kicking in at very low speeds on dry roads, ABS light illuminated

What to Inspect:
  • Visually inspect the rings through the rear wheels for cracks or missing teeth
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Buying Tips for 2005 Smart Fortwo (450)

  • ✓The 700cc engine is more robust than the 600cc but still has a limited lifespan
  • ✓Check for the "Evil Twin" SAM protection modifications on Roadster models
  • ✓Ensure the G-Box shifts through all gears using both stick and paddles
2003–20042006–2007
Check a 2005 Smart Fortwo (450) by Registration