P0301 Subaru Outback
Cylinder 1 Misfire Detected · Powertrain Code · High · Repair: Easy
What is P0301?
Misfire detected in cylinder 1. Typically caused by a worn spark plug, bad ignition coil, faulty fuel injector, or low compression in that cylinder.
When the Subaru Outback triggers code P0301 (cylinder 1 misfire detected), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the Subaru Outback.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Subaru Outback.
Common Causes on Subaru Outback
- Ignition coil failure on cylinder 1 on FB25 or FA24T Boxer engine
- Spark plug fouled from head gasket coolant or oil weepage into cylinder 1
- Fuel injector clogged or failing on cylinder 1
- Head gasket external or internal leak on cylinder 1 (classic Subaru issue)
Symptoms
- Rough idle with noticeable engine vibration
- Engine shaking or vibration especially at idle
- Loss of power during acceleration
- Check engine light flashing (indicating catalytic converter damage risk)
- Poor fuel economy from unburned fuel
- Unburned fuel smell from exhaust
Notes for Subaru Outback
Subaru Boxer head gasket leaks can cause persistent cylinder misfires; perform leak-down test if recurring.