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DTC codes / Honda codes / P1305

P1305 · HondaCylinder 5 Misfire

P1305 on a Honda means the powertrain control module has detected a misfire specifically on cylinder number 5, usually by monitoring crankshaft speed fluctuations that occur when that cylinder fails to contribute power. The code is stored when the misfire count exceeds a threshold that can damage the catalytic converter, so the computer is flagging a real combustion problem rather than a sensor glitch.

SystemPowertrain
Code typeHonda specific
SeverityHigh
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • A flashing or steady check engine light, with flashing indicating a misfire severe enough to damage the catalytic converter
  • Noticeable engine shaking or rough idle, especially when the engine is cold or under light load
  • A distinct loss of power and sluggish acceleration because one of six cylinders is not pulling its weight
  • A pulsing or vibrating sensation through the steering wheel and floorboard that worsens with engine speed
  • Often no symptoms besides the warning light when the misfire is intermittent or only occurs under specific conditions
  • A raw fuel smell from the exhaust if unburned fuel is passing through the engine

Common causes, most likely first

  1. A worn or fouled spark plug on cylinder 5, which is the most common cause on higher-mileage Honda V6 engines
  2. A failing ignition coil on cylinder 5, particularly on Honda J-series V6 engines where coil failure is a known pattern
  3. A clogged or failed fuel injector for cylinder 5, delivering too little or no fuel to that cylinder
  4. Low compression on cylinder 5 caused by valve clearance problems, a burned valve, or worn piston rings
  5. A vacuum leak near the intake runner for cylinder 5, leaning out that cylinder more than the others
  6. A damaged or corroded wiring connector or harness at the cylinder 5 coil or injector
  7. Mechanical valve train issues such as a collapsed lifter or incorrect valve adjustment on that cylinder

How to diagnose and fix it

  1. Scan all stored and pending codes with a capable scan tool and record freeze-frame data to see the conditions when the misfire was set
  2. Swap the cylinder 5 ignition coil with a neighbouring cylinder and see if the misfire follows the coil, which confirms a bad coil without buying parts
  3. Remove and inspect the cylinder 5 spark plug for fouling, wear, or incorrect gap, and replace it if worn or damaged
  4. Perform a compression test and, if compression is low, a cylinder leak-down test to rule out mechanical valve or ring problems
  5. Check the cylinder 5 fuel injector for resistance and pulse with a noid light, and test fuel pressure to rule out a weak injector or supply issue
  6. Inspect the coil and injector wiring and connectors for corrosion, chafing, or loose pins, and repair any damaged sections
  7. After repairs, clear the codes and perform a misfire monitor drive cycle to confirm the counter stays at zero before returning the vehicle

What Honda V6 Owners Miss About P1305

  • On Honda V6 engines, a P1305 is frequently accompanied by a P0305 generic misfire code, and the manufacturer-specific code often carries the more precise cylinder identification that guides the repair.
  • A misfire that only appears when the engine is cold or under light throttle is often caused by a failing coil or a spark plug that breaks down under load, not by a dead cylinder, so a simple swap test can save hours of diagnosis.
  • Honda valve clearance that has tightened out of specification can cause a misfire on a single cylinder without any compression loss at cranking speed, so a running compression test or valve adjustment check is worth doing when ignition and fuel checks pass.
  • A flashing check engine light with P1305 means the misfire is actively dumping unburned fuel into the exhaust, and continuing to drive can overheat and destroy the catalytic converter within a short distance.
  • A vacuum leak at the intake manifold gasket near cylinder 5 can lean out that cylinder enough to set a misfire code while the other cylinders run normally, so a smoke test of the intake is a smart step before replacing ignition parts.

Can I keep driving with P1305?

If the check engine light is flashing, stop driving as soon as it is safe because the misfire is dumping raw fuel into the catalytic converter and can destroy it quickly. A steady light with mild symptoms allows a short, gentle drive to a repair shop, but avoid hard acceleration and heavy loads until the misfire is fixed.

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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