What does code P0303 mean on a Subaru and is it safe to drive?
P0303: Cylinder 3 Misfire Detected. Here's what it means on your Subaru, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
What this code means
The PCM has detected a misfire specifically on cylinder 3. Diagnosis follows the same steps as P0301—swap parts to the same position on a known-good cylinder to isolate the fault.
Common causes for your Subaru
- Worn or fouled spark plug on cylinder 3
- Failing ignition coil on cylinder 3
- Leaking or clogged fuel injector
- Low compression on cylinder 3
Symptoms
- Check Engine Light, often flashing under load
- Rough idle or shaking
- Loss of power, hesitation
Typical fixes
- Replace spark plug and coil on cylinder 3
- Test and replace fuel injector
- Compression test if ignition parts don't resolve it
Repair cost range
For a Subaru, repairs for P0303 often fall between $150 and $900, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Subaru
EJ-series Subaru P0303 should prompt a head gasket check before any other diagnosis. Cylinder 3 on the rear-right of Subaru's boxer layout is one of the most common head gasket failure points on EJ251 and EJ253 engines.
Most commonly affected models