P0303 on Fiat: Causes, Symptoms and Fix Cost
Quick Answer
Not safe to drive
P0303 on a Fiat tells you that your engine's control unit has detected repeated misfires specifically in cylinder 3. This code isolates the fault to that particular cylinder's spark plug, ignition coil, fuel injector, or internal compression, allowing a much more focused and efficient diagnosis than a random misfire code.
- Severity
- High · Misfire
- Typical repair cost, all makes
- €35-€1900
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Fiat and Skanyx tells you what P0303 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0303 mean on a Fiat?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Fiat models that log P0303.
Fiat 500
2007-2024
The 0.9 TwinAir is a two-cylinder engine, so it cannot set P0303; the 1.2 Fire and 1.4 Fire four-cylinder engines can. On those, start with the cylinder 3 coil and spark plug and swap the coil with a neighbouring cylinder to see whether the misfire follows it.
Source: en.wikipedia.org
Sources
- en.wikipedia.org en.wikipedia.org/wiki/Fiat_500_(2007)
What causes P0303 on a Fiat?
Beyond the generic causes listed on the main P0303 page, these are the patterns noted for Fiat models:
Worn ignition coil on cylinder 3
: Fiat 500
Worn or overdue spark plug on cylinder 3
: Fiat 500
How to diagnose P0303 on a Fiat with OBD2
- Scan for additional codes and review freeze-frame data for engine conditions at the time of the misfire
- Swap the ignition coil from cylinder 3 to another cylinder, clear the codes, and drive. If the misfire moves with the coil, it is the cause
- Pull the spark plug from cylinder 3 and inspect for abnormal wear, oil fouling, or incorrect gap. Replace if overdue or damaged
- Test the fuel injector on cylinder 3 with a noid light to confirm electrical signal, and check spray pattern if accessible
- Perform a compression test on cylinder 3 and a leak-down test if compression is low to determine whether the issue is valves, rings, or head gasket
How much does P0303 cost to fix on a Fiat? (EUR)
Estimated repair costs for P0303 in EUR, compiled across makes. Fiat costs typically sit in the middle of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace spark plug (cylinder 3) | €5–€25 | €30–€100 | €35–€125 | Easy |
| Replace ignition coil (cylinder 3) | €25–€130 | €30–€100 | €55–€230 | Easy |
| Replace fuel injector (cylinder 3) | €50–€200 | €60–€220 | €110–€420 | Moderate |
| Compression-related repair (valves, head gasket) | €150–€600 | €400–€1300 | €550–€1900 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0303
These codes are often seen alongside P0303 or point to related issues, on any make:
Looking for the full P0303 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0303 guide