IsItAGoodCar
Reliability Guide

Common Problems with the
2003–2004 Smart Fortwo (450)

We've identified 4 known issues that can affect the 2003–2004 Smart Fortwo (450). 3 of these are serious faults that could be expensive to repair.

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
Verified by IsItAGoodCar Research Team

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
Verified by IsItAGoodCar Research Team

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
Verified by IsItAGoodCar Research Team

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
Verified by IsItAGoodCar Research Team

Buying Tips for 2003–2004 Smart Fortwo (450)

  • ✓Prioritize cars with a documented engine rebuild if the mileage is over 60,000; the small turbo engines burn oil and lose compression quickly.
  • ✓Pull back the carpets in both footwells to check for moisture; leaking windscreens frequently destroy the SAM unit (fuse box) underneath.
  • ✓Check that all six spark plugs (two per cylinder) have been changed; garages often ignore the difficult-to-reach lower three.
  • ✓Ensure the automated manual gearbox shifts through all gears; clutch actuators frequently seize and require adjustment or replacement.
  • ✓Inspect the plastic body panels for cracking, particularly around the front bumper and wheel arches.
  • ✓Look for heavy oil misting around the turbocharger and intercooler piping, indicating impending turbo failure.
1999–20022005
Check a 2003–2004 Smart Fortwo (450) by Registration