Worn or fouled spark plug in cylinder 1; Faulty ignition coil or spark plug wire for cylinder 1; Clogged or leaking fuel injector on cylinder 1; Vacuum leak at the intake manifold near cylinder 1; Low compression due to worn piston rings, valves, or head gasket; Faulty rocker arm or valve adjustment issue specific to cylinder 1; Engine mechanical problem such as a collapsed lifter or damaged camshaft lobe

DTC codes / Honda codes / P1201

P1201 · HondaCylinder 1 Misfire

Q: What does code P1201 mean?

Cylinder 1 Misfire. P1201 is a Honda-specific code indicating that the powertrain control module has detected a misfire on cylinder 1, typically by monitoring crankshaft speed fluctuations. The computer sets this code when the misfire rate exceeds a threshold that could damage the catalytic converter or affect emissions.

P1201 is a Honda-specific code indicating that the powertrain control module has detected a misfire on cylinder 1, typically by monitoring crankshaft speed fluctuations. The computer sets this code when the misfire rate exceeds a threshold that could damage the catalytic converter or affect emissions.

SystemPowertrain

Code typeHonda specific

SeverityHigh

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Check engine light illuminated, often flashing if the misfire is severe
Rough idle or shaking felt through the steering wheel and seats
Noticeable loss of power or hesitation during acceleration
Engine vibration that worsens under load, such as climbing a hill
Often no symptoms besides the warning light, especially with a mild misfire
Poor fuel economy or a rotten egg smell from the exhaust in severe cases

Common causes, most likely first

Worn or fouled spark plug in cylinder 1
Faulty ignition coil or spark plug wire for cylinder 1
Clogged or leaking fuel injector on cylinder 1
Vacuum leak at the intake manifold near cylinder 1
Low compression due to worn piston rings, valves, or head gasket
Faulty rocker arm or valve adjustment issue specific to cylinder 1
Engine mechanical problem such as a collapsed lifter or damaged camshaft lobe

How to diagnose and fix it

Scan all stored codes and freeze-frame data to confirm the misfire is isolated to cylinder 1
Inspect the spark plug in cylinder 1 for wear, fouling, or incorrect gap; replace if needed
Swap the ignition coil from cylinder 1 with a known-good cylinder and see if the misfire moves
Check for vacuum leaks around the intake manifold and cylinder 1 intake runner using carb cleaner or smoke
Test the fuel injector for cylinder 1 with a noid light or by listening for a consistent click
Perform a compression test and cylinder leak-down test to rule out mechanical issues
If compression is low, perform a valve adjustment or inspect the valvetrain for damage

Honda misfire traps you should not fall for

A flashing check engine light means the misfire is severe enough to damage the catalytic converter, so stop driving immediately and diagnose the cause.
Honda engines are known for valve clearance issues that can cause a single-cylinder misfire, so always check valve adjustment before replacing expensive parts.
A misfire code for cylinder 1 can be set by a failing ignition coil that tests fine when cold but breaks down under heat; swap-testing is more reliable than a simple resistance check.
Fuel injector problems on Honda engines often stem from clogged screens or internal leaks that do not always trigger a lean code, so flow testing is essential.
The P1201 code can be triggered by a loose or damaged crankshaft position sensor reluctor wheel, which mimics a misfire by sending erratic signals to the computer.

Can I keep driving with P1201?

If the check engine light is flashing, pull over and stop driving to prevent catalytic converter damage; if it is steady, drive gently to a repair shop and avoid heavy acceleration or towing.

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.