Ignition & misfire · Powertrain · generic (SAE-defined)
P0305: Cylinder 5 Misfire Detected
P0305 means the engine computer detected cylinder 5 misfiring, so that cylinder is not producing its share of power on a regular basis.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0305 sets
The powertrain control module (PCM) watches the crankshaft speed pattern for each firing event. When cylinder 5 repeatedly shows no power contribution, the PCM tallies those misfires and sets P0305 after exceeding a calibrated count. Calibrations vary by manufacturer.
Common causes of P0305
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Ignition coil or plug wire failure on cylinder 5
- Worn spark plug in cylinder 5
- Injector problem on cylinder 5
- Wiring fault in the cylinder 5 coil or injector circuit
- Intake gasket or vacuum leak on the cylinder 5 side
- Mechanical damage such as a burnt valve
P0305 symptoms
- Check engine light on or flashing
- Rough or uneven idle
- Hesitation under acceleration
- Reduced fuel economy
How P0305 is diagnosed
- Confirm the code and review freeze frame data.
- Identify where cylinder 5 sits on this engine using service information.
- Inspect and swap the cylinder 5 coil and plug to see if the misfire moves.
- Test injector operation and wiring for cylinder 5.
- Smoke-test for intake leaks on that bank.
- Run compression and leak-down tests if ignition and fuel are good.
Typical fixes for P0305
- Replace the cylinder 5 ignition coil
- Replace spark plugs
- Clean or replace the cylinder 5 injector
- Repair intake leaks
- Repair mechanical faults if compression is low
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0305 FAQ
What does code P0305 mean?
P0305 means the engine computer detected cylinder 5 misfiring, so that cylinder is not producing its share of power on a regular basis. The standard definition is "Cylinder 5 Misfire Detected."
Can I drive with a P0305 code?
Brief, gentle driving is usually acceptable while the check engine light is steady. A flashing light means stop driving soon, because raw fuel from cylinder 5 can overheat the catalytic converter.
Does P0305 only appear on engines with five or more cylinders?
Yes. A four-cylinder engine has no cylinder 5, so this code applies to five-, six-, eight-, and larger-cylinder engines.
Which bank is cylinder 5 on?
It depends on how the manufacturer numbers cylinders. On some V engines it is on bank 1 and on others bank 2, so verify with service information.
Keep researching
Engine guides by brand (known issues, specs)
More ignition & misfire codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.