Smart Fault Codes & Common Issues
Generic OBD codes rarely tell you the actual Smart-specific fault. This catalog maps each code to the Smart-specific failure pattern, links to deep guides for the most common ones, and surfaces owner-confirmed warranty notes where they exist. About 40 codes covered; 10 have full repair guides today and the rest are honest lookup-only entries that point you to the right reference.
Top guides (45 deep dives)
Full DIY write-ups with cheap-first checks, parts pricing, and citations.
Three-Bar Warning
HIGHThe 451 transmission has lost its position. Brake-pedal reteach clears most cases at zero cost before any actu…
P0303
HIGHOn the 451 M132 three-cylinder, swap coil and plug across cylinders before suspecting compression. Burned exha…
P0303
HIGHOn the 453 it is almost always a valve cover gasket leaking oil into the spark plug well. Inspect the well fir…
P0410
MEDIUMOn the 451 it is usually the SAI switchover valve (Mercedes 142147 / Smart A0025401497). Cheap part, 5-minute …
P0805
HIGHSmart automated-manual clutch position sensor. Often actuator wear plus adaptation/teach-in needed before part…
P2359
MEDIUMOn a 451 CDI diesel this triggers safe mode (won't rev past 3000rpm). It is almost always a vacuum hose leak o…
NAMED-450-alternator-soft-seize
NO-STARTOn a 450 that has been sitting, the alternator pulley can soft-seize and lock the engine. Check pulley rotatio…
NAMED-451-cabrio-roof
LOWInspect the plastic roof sliders first — they are a wear part Richard Bowden suggests replacing every 4 years.…
NAMED-water-leak
MEDIUMUsually traces to window seals, the front bulkhead, or blocked door drains. The Roadster has a dedicated leak …
NAMED-window-regulator
LOWA known wear point on every Smart generation. Door panel off, regulator out, replacement in. DIY-friendly fix …
P0300
HIGHMulti-cylinder misfire on a Smart usually means a fuel-side issue (injector, fuel pressure) or coil pack arcin…
P0301
HIGHOn the M132 three-cylinder cylinder 1 is least heat-stressed. Coil/plug swap test still applies; rare to see c…
P0302
HIGHMiddle cylinder on the M132. Same cheap-first coil/plug swap order as P0303.
P0171
MEDIUMOn Smart three-cylinders, P0171 commonly traces to a vacuum/intake leak rather than fuel-side. Smoke-test the …
P0172
MEDIUMLess common than lean codes on Smart. Check for stuck-open injector or fuel pressure regulator before swapping…
P0420
MEDIUMOn Smart, P0420 is often the downstream O2 sensor before the cat itself. Test the post-cat O2 sensor switching…
P0130
LOWUpstream O2 sensor on Smart. Check connector and wiring first; sensor itself is usually the fix if signal is f…
P0135
LOWHeater element inside the upstream O2 sensor. Replace the sensor; rarely a wiring issue alone.
P0455
LOWAlmost always a loose or bad fuel cap on Smart. Reseat or replace the cap, clear the code, drive a few cycles …
P0457
LOWSmart's most fuel-cap-specific EVAP code. Reseat or replace the cap, clear, drive a few cycles.
P0442
LOWSmaller leak than P0455. Same fuel-cap-first approach, then smoke-test the EVAP system if cap is good.
P0497
MEDIUMOften a sticking purge valve or vacuum routing fault on Smart. Check valve operation with a vacuum source befo…
P0335
NO-STARTOn Smart this is usually a no-start or stalls-when-hot pattern. Sensor and connector first; flywheel reluctor …
P0336
MEDIUMIntermittent CKP signal — often shows as random stall and restart. Check sensor and wiring before swapping; re…
P0340
MEDIUMCam sensor on Smart is usually the cheap fix; check connector and harness routing for chafe before swap.
P0072
MEDIUMOn Smart this often surfaces with cluster oddities. Check the instrument cluster connector and sensor harness …
P0562
MEDIUMSmart is sensitive to low battery voltage — many phantom codes trace back here. Load-test the battery and chec…
P0563
MEDIUMUsually a regulator-side alternator fault. Check charging voltage at idle and 2000rpm before swapping alternat…
U0100
HIGHOn Smart, U-codes often follow a flat battery or jump-start event. Check battery health and CAN bus connectors…
P2022
HIGHOn 451 transmissions this is a clutch system fault paired with the three-bar warning. See the P0805 deep guide…
P202A
HIGHSmart-known clutch actuator code. Often paired with P0805 / P2022 and the three-bar warning. Same actuator fam…
P2034
HIGHOften surfaces alongside the three-bar transmission warning on the 451. Try the brake-pedal reteach before sus…
P0234
MEDIUMOn a 451 Brabus or CDI this is usually a stuck wastegate actuator or boost solenoid, not a failed turbo. Check…
P0299
MEDIUMUsually a boost leak — split intercooler hose or loose clamp on Smart turbos. Pressure-test the charge pipe be…
P0117
LOWCheap sensor swap on Smart. Check connector for corrosion before swap; harness chafe near the thermostat housi…
P0128
LOWAlmost always a thermostat stuck open on Smart. Replace the thermostat — symptom is slow warm-up and weak cabi…
C1000
SAFETYGeneric ABS control module code. On Smart, low battery voltage during drive cycles can latch this — load-test …
C1020
SAFETYFront wheel speed sensor on Smart. Inspect the connector at the strut — water and salt corrode them. Cheap sen…
P0128-453
MEDIUM453 uses a Getrag dual-clutch gearbox; harsh shifts often clear after a software update / adaptation. Try a de…
P0741
MEDIUMRare on Smart since most variants are not torque-converter automatics; on 453 DCT this can surface from a soft…
P0102
MEDIUMSmart MAF sensors are sensitive to oil from over-oiled aftermarket filters. Clean the MAF before swap; check a…
B00A068
SAFETYPassenger-seat occupant weight sensor (OCS) fault on the 453. Triggers airbag warning light + 'Malfunction vis…
B00A07B
SAFETYCompanion code to B00A068 / B00A096. Same passenger-seat occupant weight sensor system, different signal chann…
B00A096
SAFETYThird companion code in the 453 OCS cluster (with B00A068 and B00A07B). Treat as one fault, not three separate…
B152014
HIGHF2K5 is the starter relay in the 453 SAM (Signal Acquisition Module). Short to ground typically means the rela…
Full catalog (45 entries)
Quick lookup for any Smart code we have notes on. Filter by system, severity, or model. Codes without a deep guide link out to FQ101, Evilution, or OBD-codes.com.
| Code | System | Severity | Models | Smart-specific note | Warranty | Action |
|---|---|---|---|---|---|---|
| Three-Bar Warning | Clutch & gearbox | High | 451 | The 451 transmission has lost its position. Brake-pedal reteach clears most cases at zero cost before any actuator parts swap. | — | Read the guide → |
| P0303 | Misfire | High | 451 | On the 451 M132 three-cylinder, swap coil and plug across cylinders before suspecting compression. Burned exhaust valve on cyl 3 is the worst-case but not the starting point. | — | Read the guide → |
| P0303 | Misfire | High | 453 | On the 453 it is almost always a valve cover gasket leaking oil into the spark plug well. Inspect the well first; the fix is the gasket, not just plugs. | — | Read the guide → |
| P0410 | Secondary air | Medium | 451 | On the 451 it is usually the SAI switchover valve (Mercedes 142147 / Smart A0025401497). Cheap part, 5-minute swap. Replace the valve before going after the pump. | Often covered | Read the guide → |
| P0805 | Clutch & gearbox | High | 451 | Smart automated-manual clutch position sensor. Often actuator wear plus adaptation/teach-in needed before parts cannon. Commonly paired with the three-bar warning past 100k miles. | Possibly / context | Read the guide → |
| P2359 | EGR / vacuum | Medium | 451 | On a 451 CDI diesel this triggers safe mode (won't rev past 3000rpm). It is almost always a vacuum hose leak or check valve failure, not the EGR valve itself. | — | Read the guide → |
| Alternator soft-seize | Crank / no-start | No-start | 450 | On a 450 that has been sitting, the alternator pulley can soft-seize and lock the engine. Check pulley rotation by hand before suspecting starter. Free fix without removal. | — | Read the guide → |
| Cabrio roof | Named mechanical | Low | 451 | Inspect the plastic roof sliders first — they are a wear part Richard Bowden suggests replacing every 4 years. Cheap and DIY-friendly before suspecting the motor. | — | Read the guide → |
| Water leak | Water / leaks | Medium | 450451452 | Usually traces to window seals, the front bulkhead, or blocked door drains. The Roadster has a dedicated leak guide because the problem is so common. | — | Read the guide → |
| Window regulator | Named mechanical | Low | 450451453 | A known wear point on every Smart generation. Door panel off, regulator out, replacement in. DIY-friendly fix with the right plastic clips and patience. | — | Read the guide → |
| P0300 | Misfire | High | 451453 | Multi-cylinder misfire on a Smart usually means a fuel-side issue (injector, fuel pressure) or coil pack arcing across cylinders. Check coil pack and plugs as a set before chasing fuel. | — | Read the guide → |
| P0301 | Misfire | High | 451453 | On the M132 three-cylinder cylinder 1 is least heat-stressed. Coil/plug swap test still applies; rare to see compression issues here. | — | Read the guide → |
| P0302 | Misfire | High | 451453 | Middle cylinder on the M132. Same cheap-first coil/plug swap order as P0303. | — | Read the guide → |
| P0171 | Fuel trim | Medium | 451453 | On Smart three-cylinders, P0171 commonly traces to a vacuum/intake leak rather than fuel-side. Smoke-test the intake before swapping MAF or injectors. | — | Read the guide → |
| P0172 | Fuel trim | Medium | 451453 | Less common than lean codes on Smart. Check for stuck-open injector or fuel pressure regulator before swapping the MAF. | — | Read the guide → |
| P0420 | O2 sensor | Medium | 451453 | On Smart, P0420 is often the downstream O2 sensor before the cat itself. Test the post-cat O2 sensor switching pattern with a scan tool before quoting a cat. | — | Read the guide → |
| P0130 | O2 sensor | Low | 451453 | Upstream O2 sensor on Smart. Check connector and wiring first; sensor itself is usually the fix if signal is flat-lined. | — | Read the guide → |
| P0135 | O2 sensor | Low | 451453 | Heater element inside the upstream O2 sensor. Replace the sensor; rarely a wiring issue alone. | — | Read the guide → |
| P0455 | EVAP | Low | 451453 | Almost always a loose or bad fuel cap on Smart. Reseat or replace the cap, clear the code, drive a few cycles before any deeper EVAP work. | Possibly / context | Read the guide → |
| P0457 | EVAP | Low | 451453 | Smart's most fuel-cap-specific EVAP code. Reseat or replace the cap, clear, drive a few cycles. | Possibly / context | Read the guide → |
| P0442 | EVAP | Low | 451453 | Smaller leak than P0455. Same fuel-cap-first approach, then smoke-test the EVAP system if cap is good. | — | Read the guide → |
| P0497 | EVAP | Medium | 451453 | Often a sticking purge valve or vacuum routing fault on Smart. Check valve operation with a vacuum source before parts swap. | Often covered | Read the guide → |
| P0335 | Crank / no-start | No-start | 451453 | On Smart this is usually a no-start or stalls-when-hot pattern. Sensor and connector first; flywheel reluctor damage is rare but possible. | — | Read the guide → |
| P0336 | Crank / no-start | Medium | 451453 | Intermittent CKP signal — often shows as random stall and restart. Check sensor and wiring before swapping; reluctor damage is the worst-case. | Often covered | Read the guide → |
| P0340 | Crank / no-start | Medium | 451453 | Cam sensor on Smart is usually the cheap fix; check connector and harness routing for chafe before swap. | — | Read the guide → |
| P0072 | Voltage / CAN | Medium | 451453 | On Smart this often surfaces with cluster oddities. Check the instrument cluster connector and sensor harness before deeper diagnosis. | Possibly / context | Read the guide → |
| P0562 | Voltage / CAN | Medium | 451453 | Smart is sensitive to low battery voltage — many phantom codes trace back here. Load-test the battery and check alternator output before chasing other symptoms. | — | Read the guide → |
| P0563 | Voltage / CAN | Medium | 451453 | Usually a regulator-side alternator fault. Check charging voltage at idle and 2000rpm before swapping alternator. | — | Read the guide → |
| U0100 | Voltage / CAN | High | 451453 | On Smart, U-codes often follow a flat battery or jump-start event. Check battery health and CAN bus connectors before suspecting ECU. | — | Read the guide → |
| P2022 | Clutch & gearbox | High | 451 | On 451 transmissions this is a clutch system fault paired with the three-bar warning. See the P0805 deep guide; same actuator family. | — | Read the guide → |
| P202A | Clutch & gearbox | High | 451 | Smart-known clutch actuator code. Often paired with P0805 / P2022 and the three-bar warning. Same actuator family. | — | Read the guide → |
| P2034 | Clutch & gearbox | High | 451 | Often surfaces alongside the three-bar transmission warning on the 451. Try the brake-pedal reteach before suspecting the gear position sensor. | — | Read the guide → |
| P0234 | Turbo / boost | Medium | 451 | On a 451 Brabus or CDI this is usually a stuck wastegate actuator or boost solenoid, not a failed turbo. Check actuator linkage by hand before parts. | — | Read the guide → |
| P0299 | Turbo / boost | Medium | 451 | Usually a boost leak — split intercooler hose or loose clamp on Smart turbos. Pressure-test the charge pipe before suspecting the turbo. | — | Read the guide → |
| P0117 | Cooling | Low | 451453 | Cheap sensor swap on Smart. Check connector for corrosion before swap; harness chafe near the thermostat housing is occasional. | — | Read the guide → |
| P0128 | Cooling | Low | 451453 | Almost always a thermostat stuck open on Smart. Replace the thermostat — symptom is slow warm-up and weak cabin heat. | — | Read the guide → |
| C1000 | ABS / ESP | Safety | 451453 | Generic ABS control module code. On Smart, low battery voltage during drive cycles can latch this — load-test the battery before parts. | — | Read the guide → |
| C1020 | ABS / ESP | Safety | 451453 | Front wheel speed sensor on Smart. Inspect the connector at the strut — water and salt corrode them. Cheap sensor swap once you confirm. | — | Read the guide → |
| P0128-453 | Transmission | Medium | 453 | 453 uses a Getrag dual-clutch gearbox; harsh shifts often clear after a software update / adaptation. Try a dealer adaptation drive cycle before quoting clutch packs. | — | Read the guide → |
| P0741 | Transmission | Medium | 453 | Rare on Smart since most variants are not torque-converter automatics; on 453 DCT this can surface from a software-side adaptation issue more than mechanical. | — | Read the guide → |
| P0102 | Fuel trim | Medium | 451453 | Smart MAF sensors are sensitive to oil from over-oiled aftermarket filters. Clean the MAF before swap; check air filter housing for moisture. | — | Read the guide → |
| B00A068 | Airbag / SRS | Safety | 453 | Passenger-seat occupant weight sensor (OCS) fault on the 453. Triggers airbag warning light + 'Malfunction visit workshop' message. Often surfaces alongside B00A07B and B00A096 — they are the same control unit reporting on different signal paths. Don't ignore: the passenger airbag deployment logic depends on this sensor. | Possibly | Read the guide → |
| B00A07B | Airbag / SRS | Safety | 453 | Companion code to B00A068 / B00A096. Same passenger-seat occupant weight sensor system, different signal channel. If you see one, you usually see the others — clear them and they come back unless the underlying connector or module is fixed. | Possibly | Read the guide → |
| B00A096 | Airbag / SRS | Safety | 453 | Third companion code in the 453 OCS cluster (with B00A068 and B00A07B). Treat as one fault, not three separate ones — start with the seat connector under the passenger seat before suspecting the module. | Possibly | Read the guide → |
| B152014 | Voltage / CAN | High | 453 | F2K5 is the starter relay in the 453 SAM (Signal Acquisition Module). Short to ground typically means the relay coil itself failed, the relay is welded closed, or the harness to the relay has chafed. Can cause intermittent no-crank or persistent crank-after-start. | — | Read the guide → |
| No codes match those filters. Try resetting or broadening your search. | ||||||
Lookup-only rows are honest about being lookup-only — they point at FQ101, Evilution, or OBD-codes.com so you can cross-reference. Have a Smart-specific failure pattern for one of these codes? Email us and we'll fold it in.