P0301 on a Honda Civic
P0301 means cylinder 1 Misfire Detected. On the Civic, a few causes come up far more than others.
What P0301 usually means on a Civic
P0301 pins a misfire specifically to cylinder 1. On the Civic that most often traces to the coil or plug for that cylinder rather than anything engine-wide. Swapping the No. 1 coil with a neighbor is the fastest way to confirm. Left alone, a single-cylinder misfire can overheat and ruin the catalytic converter.
Most common causes on the Civic
- Failed coil-on-plug for cylinder 1
Individual coils fail one at a time on the Civic; the code follows the coil if you swap it.
- Worn or fouled spark plug
A single fouled iridium plug commonly sets a lone-cylinder code near its service interval.
- Injector fault on cylinder 1
Less common, but a clogged or leaking injector isolates the misfire to one hole.
- Low compression on cylinder 1
High-mileage engines can develop a burnt valve or ring wear localized to one cylinder.
What P0301 costs to fix on a Civic
Because the coils and plugs are exposed on top of the transverse four, replacing a single coil is a quick, inexpensive job - often well under one hundred dollars in parts. Diagnosis is cheap since a coil/plug swap test confirms it without special tools. Only if compression is low does the bill climb.
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.
Other codes on the Honda Civic
Related symptoms
Honda Civic 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 Civic?
Every problem becomes a Case. Tell Redline what your Civic 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.