Worn or fouled spark plug in cylinder 1, especially on older Honda engines with high mileage; Failed ignition coil or coil-on-plug boot for cylinder 1; Faulty fuel injector for cylinder 1, including clogged nozzle or electrical failure; Vacuum leak at the intake manifold runner or injector seal specific to cylinder 1; Low compression on cylinder 1 from worn rings, burned valve, or head gasket issue; Valve clearance out of specification on engines with adjustable valves, common on older Honda four-cylinders; Wiring or connector fault in the cylinder 1 injector or coil circuit

DTC codes / Honda codes / P1301

P1301 · HondaCylinder 1 Misfire

Q: What does code P1301 mean?

Cylinder 1 Misfire. P1301 on a Honda means the powertrain control module (PCM) has detected a misfire specifically on cylinder 1, based on crankshaft speed fluctuations that deviate from the expected firing pattern. The PCM monitors the crankshaft position sensor signal and flags this code when cylinder 1 fails to contribute its share of engine torque, often counting misfire events over a specific drive cycle.

P1301 on a Honda means the powertrain control module (PCM) has detected a misfire specifically on cylinder 1, based on crankshaft speed fluctuations that deviate from the expected firing pattern. The PCM monitors the crankshaft position sensor signal and flags this code when cylinder 1 fails to contribute its share of engine torque, often counting misfire events over a specific drive cycle.

SystemPowertrain

Code typeHonda specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Check Engine Light illuminated, often flashing if the misfire is severe enough to risk catalytic converter damage
Noticeable engine shake or vibration at idle, especially when cold
Rough running or hesitation during acceleration
Loss of power and reduced fuel economy
Often no symptoms besides the warning light when the misfire is intermittent or mild
A sulfur or rotten egg smell from the exhaust if unburned fuel is reaching the catalytic converter

Common causes, most likely first

Worn or fouled spark plug in cylinder 1, especially on older Honda engines with high mileage
Failed ignition coil or coil-on-plug boot for cylinder 1
Faulty fuel injector for cylinder 1, including clogged nozzle or electrical failure
Vacuum leak at the intake manifold runner or injector seal specific to cylinder 1
Low compression on cylinder 1 from worn rings, burned valve, or head gasket issue
Valve clearance out of specification on engines with adjustable valves, common on older Honda four-cylinders
Wiring or connector fault in the cylinder 1 injector or coil circuit

How to diagnose and fix it

Scan all stored and pending codes with a capable scan tool to confirm P1301 is the only misfire code and check for related codes like P0301
Inspect the spark plug in cylinder 1 for fouling, wear, or incorrect gap, and replace if worn
Swap the ignition coil from cylinder 1 with another cylinder and see if the misfire follows the coil
Perform a cylinder balance test or use a scan tool with misfire counters to verify which cylinder is actually misfiring
Check fuel injector operation with a noid light or listen for clicking, and test injector resistance if accessible
Run a compression test and, if low, a leak-down test on cylinder 1 to rule out mechanical faults
Inspect intake manifold gaskets and vacuum lines near cylinder 1 for leaks using a smoke machine or carb cleaner

Honda Cylinder 1 Misfire Diagnosis Traps

A P1301 can be set by a marginal ignition coil that tests fine when cold but breaks down under load, so always swap-test the coil rather than relying on a bench test.
Honda engines with adjustable valve clearances can develop a misfire on one cylinder when the exhaust valve clearance tightens, and this often does not show up as low compression until the valve burns.
The PCM may set P1301 without illuminating the Check Engine Light if the misfire count is below the threshold for a hard fault, so a pending code scan is essential.
A dirty or failing mass airflow sensor can cause a lean condition that affects cylinder 1 first due to intake manifold design, so check fuel trims before condemning ignition parts.
After replacing a spark plug or coil, the PCM may need several drive cycles to clear the misfire counter, so do not assume the repair failed if the light stays on briefly.

Can I keep driving with P1301?

You can drive a short distance to a repair shop if the misfire is mild and the Check Engine Light is steady, but avoid hard acceleration and sustained highway speeds. If the light is flashing, stop driving immediately because unburned fuel can overheat and destroy the catalytic converter.

Tools that help

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Guidance is general and written for Honda vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.