Home Maintenance Quick reference

Smart Fortwo and Forfour 453 Fuse Quick-Reference

Easy 2-10 min $0-15 (assorted fuses + plastic puller)Smart Fortwo 453Smart Forfour 453

Service interval: Inspect on symptom — not a service item

Tools you'll need

  • Plastic fuse puller (the small one — 453 uses some micro2 positions)
  • Phone flashlight
  • Spare mini blade fuses (5, 7.5, 10, 15, 20, 25, 30A)
  • Spare micro2 low-profile fuses (5, 7.5, 10, 15A)

What this is + why it matters

The 453 carries more electronics than any Smart that came before it. More cameras, more sensors, more comfort logic, an electric park brake, start-stop, and on the EQ a high-voltage system layered on top of all of it. More electronics means more fuses, and more fuses means more weird-symptom-from-blown-fuse opportunities — a dead USB port that takes the infotainment with it, a blown ABS feed that lights three warnings at once, an aux-battery circuit dropout that mimics a bad main battery.

The 453 also leans heavily on the SAM module for relay logic. That's why fault codes like B152014 (F2K5 starter relay) point at the F2 interior fuse and relay module, not at a relay you can hold in your hand. This page is the 453-specific fuse reference — it pairs with the cross-chassis fuse box layout page and the SAM module overview. Use it to find the right fuse for a dead circuit, and to know which fuses are owner-territory versus shop-territory.

Verify against the legend printed inside your fuse cover. Positions and ratings vary by build year, market (US/EU/UK), drivetrain (gas/EQ), and trim. The values below are community-typical for a 453 — confirm against the diagram on your specific car before swapping anything.

What you'll need

The 453 fuse boxes split into two:

  • F1 — engine compartment fuse and relay module. Lives under the rear hood next to the engine. Owner-accessible. Most of the fuses you'll actually pull are here.
  • F2 — vehicle interior fuse and relay module. Lives behind the dash trim on the driver's side. Shop territory. Relays inside (F2K5 starter, etc.) are SAM-driven and not pull-and-swap.

F1 — engine compartment (owner-accessible, typical positions)

Position Amp Circuit / what it feeds
F1f1 40A Cooling fan main feed
F1f2 30A Headlight low beam (left + right combined feed)
F1f3 verify Headlight high beam
F1f4 15A Fuel pump
F1f5 10A Engine ECU power
F1f6 15A Ignition coils
F1f7 verify DCT (twinamic) control unit
F1f8 7.5A ABS / ESP module logic
F1f9 30A ABS / ESP pump motor
F1f10 verify Wiper motor
F1f11 verify Horn
F1f12 verify AC clutch / compressor control
F1f13 verify Rear defrost
F1f14 verify Aux battery charging (453 EQ only — verify, this position varies)

F2 — vehicle interior (mostly shop territory, but you'll see these called out in symptom diagnosis)

Position Amp Circuit / what it feeds
F2f1 verify Cigarette lighter / 12V outlet
F2f2 verify Infotainment / radio head unit
F2f3 verify USB ports (front)
F2f4 verify Instrument cluster
F2f5 verify Central locking
F2f6 verify Power windows
F2f7 verify Electric park brake (EPB)
F2f8 verify Brake light feed
F2f9 verify Comfort access / key fob receiver
F2f10 verify Interior lighting
F2f11 verify Heated seats (if equipped)

F2 relays (NOT user-replaceable — SAM-driven)

Relay ID Function Notes
F2K5 Starter relay The one behind the B152014 fault code. Not a swap.
F2K1, F2K2 SAM-controlled body relays Live inside the F2 module. Diagnosis only.

Step by step

This is a reference page — the actual fuse-pulling procedure is short.

  1. Identify the dead circuit. Write down what dropped out. "Both headlights low beam dead" maps to a different fuse than "passenger-side parking light only." Specificity saves time.
  2. Open F1 first. Lift the rear hood, pop the F1 cover. The diagram is printed on the inside of the cover on most builds. If yours is rubbed off, the workshop manual has the same chart.
  3. Use the right puller. The 453 mixes mini blade fuses with micro2 low-profile fuses in some positions. Micro2 is physically smaller — a standard mini-blade puller will not grip a micro2 fuse. The plastic puller clipped inside the F1 cover usually fits both, or carry a dedicated micro2 puller.
  4. Pull the suspect fuse straight up. Hold it to a light. Broken metal strip = blown. Replace only with the same amp rating and the same fuse type (mini blade vs micro2 — they are not interchangeable).
  5. If the symptom maps to F2 territory — interior accessories, EPB, comfort access, starter logic — stop here. F2 work needs a Smart-experienced shop with Star Diagnosis or equivalent. F2 relays are not pull-and-swap.
  6. If F1 looks clean and the circuit is still dead, the SAM is the next suspect, not another fuse. See the SAM module overview.

Common gotchas

A repeat-blowing fuse means there's a short downstream. Stop. Don't keep feeding fuses into a shorted circuit — at minimum you waste fuses, at worst you melt insulation. Trace the short first, or take it to a shop.

SAM-driven F2 relays are a common cause of intermittent no-start on the 453. F2K5 — the starter relay — fails inside the module and shows up as a B152014 code. There's no replaceable relay to swap. The fix is SAM/F2 diagnosis, often module-level work. See the B152014 F2K5 starter relay page for the full chase.

The 453 EQ fuse box has additional positions for HV-related circuits. Orange-jacketed fuses or orange-sleeved wiring near the fuse box mean high-voltage system, do not touch. These are not 12V fuses you swap on the driveway. If the orange caught your eye while you were looking for the fuel pump fuse, you're on the wrong page of the diagram.

Don't mix fuse types. Mini blade and micro2 look similar at a glance but are different sizes. Forcing a mini-blade into a micro2 socket damages the socket. Forcing a micro2 into a mini-blade socket gives you a fuse that wobbles and doesn't make full contact — the circuit will work intermittently and you'll chase a ghost.

Aux battery on the 453 EQ has its own circuit. A weak aux battery can light up SAM codes that look like F1 fuse problems. Battery-first the same way you would on the 451 — see auxiliary battery 453.

Standard mini blade colors: tan/5A, brown/7.5A, red/10A, blue/15A, yellow/20A, clear/25A, green/30A. Useful eyeball check, but always confirm the printed number on the fuse body — color alone is not authoritative.

When to skip DIY

Anything orange on a 453 EQ. Stop. Orange = high-voltage. The HV system on the EQ runs at hundreds of volts DC and is not touched without proper PPE and de-energization procedure. Owner-territory ends where the orange begins.

The F2 module is shop work. If the symptom narrows to F2 — starter relay, EPB, comfort access, central locking gone weird — that's a diagnosis job for a Smart-experienced shop. The relays inside the module are SAM-driven and pair-coded to the car. There is no driveway swap.

SAM module replacement on the 453 is not a parts-swap fix. A used SAM dropped in without coding throws codes from day one. If diagnosis lands on the SAM, it goes to a shop that can code the new module to the VIN.

A circuit that keeps blowing fuses no matter what is a short-to-ground hunting expedition. Possible on the driveway with patience and a multimeter, but a shop with proper gear finds it faster. Pay for the diagnosis, then decide whether to do the repair yourself.

Heat damage on the fuse box itself — melted plastic around a slot, discoloration on bus bars, brown haze around a contact — means the panel needs to come out, not another fuse. Heated fuse boxes are how cars catch fire. Don't keep using one.

Manual references

Top reference manuals for this chassis (from our catalog of 88 Smart manuals):

Need something specific? Browse all 88 manuals by chassis, year, region, or document type.

Related fault codes

Related maintenance