P0301 on a Subaru Outback
P0301 means cylinder 1 Misfire Detected. On the Outback, a few causes come up far more than others.
What P0301 usually means on a Outback
P0301 isolates a misfire to cylinder 1 on the Outback. Most of the time it is an ignition issue on that cylinder, a failed coil or a worn plug, and the boxer's side-mounted plug location just makes it a little more work to reach. An injector fault on cylinder 1 is the next suspect. On an older EJ25, a single-cylinder misfire paired with coolant loss or white exhaust can point toward a head-gasket problem affecting that cylinder, which a compression or leak-down test will confirm.
Most common causes on the Outback
- Coil or spark plug on cylinder 1
Swap the coil to a neighboring cylinder; if the misfire follows, the coil is the cause.
- Cylinder 1 fuel injector
A clogged or failing injector starves that single cylinder and mimics an ignition fault.
- Low compression on cylinder 1
A burnt valve or, on the EJ25, head-gasket coolant intrusion shows up as a mechanical misfire.
- Vacuum leak near that cylinder
A localized leak can lean out one cylinder enough to misfire.
What P0301 costs to fix on a Outback
If it is a coil or plug, the parts are cheap; the boxer layout just adds a bit of labor to reach that side. Expect a couple hundred dollars at most for an ignition fix. If a leak-down reveals an EJ25 head-gasket issue on that cylinder, the repair jumps into the thousands, so test before you spend.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Outback owners also ask
Why is changing one coil or plug more expensive on my Outback?
The boxer engine puts the spark plugs low on the sides of the engine, so reaching them takes more labor than a plug on top of an inline engine. The part is still cheap, but plan for a little extra shop time.
How do I know if a cylinder 1 misfire is a head gasket on my EJ25?
Look for coolant loss, overheating, or white exhaust alongside the misfire, and confirm with a cooling-system pressure test and a combustion-gas (block) test. Without those symptoms, a lone P0301 is far more likely a coil, plug, or injector.
Other codes on the Subaru Outback
Related symptoms
Subaru Outback problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0301 behavior is covered on the main P0301 page. Confirm with a scan tool before buying parts.
P0301 on your Outback?
Every problem becomes a Case. Tell Redline what your Outback is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.