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DTC codes / Honda codes / P1204

P1204 · HondaCylinder 4 Misfire

P1204 on a Honda means the powertrain control module has detected a misfire specifically on cylinder 4, usually by tracking crankshaft speed fluctuations that occur when that cylinder fails to produce its share of power. The computer flags this code when the misfire count exceeds a calibrated threshold, which can range from a single hard misfire event to a recurring pattern across multiple drive cycles.

SystemPowertrain
Code typeHonda specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

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 that may smooth out as engine speed increases
  • Rough running or hesitation during acceleration, particularly under load such as climbing a hill
  • Reduced fuel economy as the engine compensates for the dead cylinder
  • A sulfur or rotten-egg smell from the exhaust if unburned fuel is reaching the catalytic converter
  • Often no symptoms besides the warning light when the misfire is intermittent or only occurs under specific conditions

Common causes, most likely first

  1. Worn or fouled spark plug in cylinder 4, including plugs with incorrect gap or the wrong heat range
  2. Failed ignition coil or coil-on-plug boot for cylinder 4, which is a common failure on Honda engines
  3. Faulty fuel injector for cylinder 4, such as a clogged nozzle or an open electrical winding
  4. Vacuum leak at the intake manifold runner or injector seal specific to cylinder 4
  5. Low compression on cylinder 4 caused by a burned valve, worn piston rings, or a head gasket breach
  6. Valve clearance out of specification on the number 4 cylinder, which is a known maintenance item on many Honda engines
  7. Wiring or connector fault in the cylinder 4 ignition coil or injector circuit

How to diagnose and fix it

  1. Scan all stored and pending codes and record freeze-frame data to confirm the misfire is isolated to cylinder 4 and not accompanied by lean or rich codes
  2. Perform a visual inspection of the cylinder 4 ignition coil, boot, and spark plug, looking for carbon tracking, oil fouling, or a cracked insulator
  3. Swap the cylinder 4 ignition coil with a known-good coil from another cylinder and recheck misfire counts to see if the fault follows the coil
  4. Remove and inspect the cylinder 4 spark plug, check its gap and condition, and replace it if worn or fouled
  5. Run a compression test and, if compression is low, perform a cylinder leak-down test to determine whether the loss is past the valves, rings, or head gasket
  6. Check valve clearance on cylinder 4 and adjust if out of specification, particularly on engines with adjustable rocker arms
  7. Test the cylinder 4 fuel injector for resistance, pulse signal, and spray pattern, and clean or replace it if faulty

Cylinder 4 misfire traps on Honda engines

  • A P1204 can be set by a misfire that only occurs during cold start or under light load, so a simple idle-only check may miss it entirely and a road test with a scan tool recording misfire counters is often required.
  • Honda engines with variable valve timing and cylinder deactivation can set a cylinder-specific misfire code when the oil pressure feeding the rocker arm assembly is low, so checking oil level and condition is a legitimate first step before condemning ignition parts.
  • Swapping the coil and plug to another cylinder is the fastest way to prove whether the fault is component-specific or rooted in the cylinder itself, and it costs nothing but time.
  • A vacuum leak at the intake manifold gasket near cylinder 4 can lean out that cylinder enough to cause a misfire without setting a lean code, so a smoke test of the intake tract is a worthwhile diagnostic step.
  • Replacing the spark plug without addressing a worn ignition coil boot or a leaking injector seal often leads to a repeat P1204 within a few thousand miles, so the root cause must be confirmed rather than guessed.

Can I keep driving with P1204?

You can drive a short distance to a repair shop if the check engine light is steady and the engine runs smoothly, but avoid hard acceleration and sustained high speeds. If the light is flashing or the engine shakes violently, stop driving because raw fuel is entering the exhaust and can destroy the catalytic converter.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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