What does code P0300 mean on a Subaru and is it safe to drive?
P0300: Random/Multiple Cylinder 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 misfires across multiple cylinders. This can cause damage to the catalytic converter if driven for long.
Common causes for your Subaru
- Worn spark plugs or ignition coils
- Clogged or bad fuel injectors
- Low compression
- Vacuum leak, bad MAF, or fuel delivery issue
Symptoms
- Check Engine Light (often flashing under load)
- Rough idle, shaking, loss of power
- Possible smell of unburned fuel
Typical fixes
- Replace spark plugs and coils as needed
- Clean or replace fuel injectors
- Fix vacuum/fuel issues
- Compression test if no obvious cause
Repair cost range
For a Subaru, repairs for P0300 often fall between $150 and $1200, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Subaru
Subaru P0300 on EJ25 SOHC naturally aspirated engines should immediately trigger a head gasket investigation—Subaru EJ25 head gaskets leak coolant into the combustion chamber causing hydrolock-style misfires. Look for white exhaust smoke, coolant loss, and elevated coolant pressure. On WRX EJ257 turbocharged, P0300 under boost is a head gasket failure until proven otherwise—this is a known failure mode and a very serious condition. On FA20 (BRZ/FR-S), P0300 is less common and usually traces to worn spark plugs or an oil separator failure.
Most commonly affected models