Ignition & misfire · Powertrain · generic (SAE-defined)
P0306: Cylinder 6 Misfire Detected
P0306 means cylinder 6 is misfiring, and the engine computer has logged enough misfire events in that cylinder to turn on the check engine light.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0306 sets
The powertrain control module (PCM) analyzes crankshaft rotation speed to detect the loss of power from a misfiring cylinder. When cylinder 6 misfires often enough within a monitoring window, P0306 is stored. The exact limits are manufacturer-specific.
Common causes of P0306
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed cylinder 6 ignition coil
- Worn or fouled cylinder 6 spark plug
- Cylinder 6 injector restriction or electrical fault
- Coolant or oil intrusion in the plug well
- Vacuum leak near cylinder 6
- Low compression in cylinder 6
P0306 symptoms
- Check engine light on or flashing
- Shaking at idle or at stops
- Loss of power
- Possible fuel smell
How P0306 is diagnosed
- Check freeze frame data and look for related codes.
- Locate cylinder 6, which on some transverse V6 engines is at the rear and harder to reach.
- Inspect the coil, plug, and plug well; swap the coil to another cylinder and retest.
- Test the cylinder 6 injector and its wiring.
- Perform a compression test on cylinder 6 if needed.
Typical fixes for P0306
- Replace the cylinder 6 coil
- Replace spark plugs
- Clean or replace the cylinder 6 injector
- Repair leaking seals or gaskets causing contamination
- Repair mechanical faults if found
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
P0306 FAQ
What does code P0306 mean?
P0306 means cylinder 6 is misfiring, and the engine computer has logged enough misfire events in that cylinder to turn on the check engine light. The standard definition is "Cylinder 6 Misfire Detected."
Can I drive with a P0306 code?
With a steady light, short careful drives are usually okay until it is repaired. If the check engine light flashes, reduce load and stop driving soon to prevent catalytic converter damage.
Why is cylinder 6 often the last place people look?
On many transverse V6 engines, cylinder 6 is on the rear bank under the intake plenum, so the coil and plug are harder to access. That access difficulty sometimes leads to skipped inspections.
Can P0306 be caused by a bad injector?
Yes. A clogged or electrically failed cylinder 6 injector will starve that cylinder of fuel and cause a misfire.
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.