P0306 Cylinder 6 Misfire
Caution
Cylinder 6 is not firing properly. Most often it is the spark plug or ignition coil on that cylinder, and a simple swap test tells you which. Do not ignore it: misfires can overheat the catalytic converter.
- Safe to drive?
- Gently, and not if the light flashes
- Typical cost at a shop
- $216-$953 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
- Carmaker bulletins
- 2 notes with links
See the cylinder 6 misfire count where your car reports it, then check it again after a coil swap.
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What it means
Each cylinder needs spark, fuel and compression to fire. P0306 means the computer saw cylinder 6 fail to fire often enough to matter. It only appears on engines with at least five cylinders: V6, V8, and some inline five and six engines. The cause is almost always on that one cylinder: its plug, its coil, its injector or, less often, its compression.
The technical version
The computer watches crankshaft speed. When a cylinder fires, the crank speeds up a little; when it misfires, it does not. P0306 sets when misfires on cylinder 6 pass a limit within a set number of revolutions. A rate high enough to harm the converter makes the light flash. P0300 sets instead when misfires move between cylinders.
Official name: Cylinder 6 Misfire Detected.
Symptoms
- Rough idle or shaking.
- Hesitation or stumble when you accelerate.
- Less power and worse fuel economy.
- A flashing check engine light under load.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A worn or fouled spark plug | most common | The plug is old, wet or damaged when you pull it. |
| A failing ignition coil | most common | Swap coil 6 with another cylinder. If the misfire code follows the coil, it is the coil. |
| A clogged or leaking fuel injector | common | Plug and coil swaps do not move the misfire. |
| A vacuum leak near that cylinder's intake runner | less common | Worse at idle, often with lean fuel trims. |
| Low compression (valve, ring or head gasket) | less common | A compression or leak-down test shows the cylinder low. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Many cars report misfire counts per cylinder (Mode 6 data). Cylinder 6 counts should be zero or near zero; a rising count confirms the code. Watch short-term fuel trim too: if it goes strongly positive at idle and settles at higher rpm, a vacuum leak is a good suspect.
What to check first, in order
-
If the light flashes, slow down and stop soon.
The converter can overheat.
What the data shows: Counts rise fast.
Cost: free
-
Pull and look at the cylinder 6 spark plug.
Cheap and often the cause.
What the data shows: After a new plug, cylinder 6 counts should drop.
Cost: $288-$399 at a shop (Spark plug replacement, RepairPal)
-
Swap coil 6 with another cylinder.
Free test of the coil.
What the data shows: If the misfire code moves (P0306 becomes P0301 or similar), replace the coil.
Cost: $238-$320 at a shop (Ignition coil replacement, RepairPal)
-
Swap-test or check the injector.
Next most likely.
What the data shows: Counts follow the injector.
Cost: $768-$953 at a shop (Fuel injector replacement, RepairPal)
-
Compression-test cylinder 6.
If spark and fuel are fine.
What the data shows: Not a scanner step.
Cost: $216-$317 at a shop (Engine compression test, RepairPal)
Is it safe to drive?
Caution
Gently, and not if the light flashes. Unburned fuel can overheat and ruin the catalytic converter.
A steady light with a small, occasional misfire: drive gently and get it fixed within days. A flashing light means the misfire is bad enough to damage the catalytic converter: slow down and stop driving as soon as it is safe. A misfire can also cost you power when you need it, for example when merging.
Stop driving and get help if
- The check engine light flashes.
- The engine shakes hard or loses power.
- You smell fuel or see heavy smoke.
What it costs
| Repair | Typical cost |
|---|---|
| Engine compression testRepairPal, updated September 3, 2026 | $216-$317 |
| Ignition coil replacementRepairPal, updated September 3, 2026 | $238-$320 |
| Spark plug replacementRepairPal, updated September 3, 2026 | $288-$399 |
| Fuel injector replacementRepairPal, updated September 3, 2026 | $768-$953 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner. Ignition coil and spark plugs together were CarMD's number 3 check engine repair in 2025 ($480), ignition coil alone number 5 ($256), spark plugs alone number 10 ($299). Fuel injectors were number 7, at an average of $572. CarMD averages come from a different method (repairs reported by its users), so they can sit below RepairPal's shop estimates.
Sources for the notes: CarMD 2026 Vehicle Health Index (press release, April 22, 2026).
Can I clear it? Will it come back?
After the repair, clear the code and drive normally for a few days. The misfire counts for cylinder 6 should stay at zero.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
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Chrysler, Dodge, Jeep 2011-2013 models with the 3.6L V6 (Journey, 200, Avenger, Challenger, Charger, 300, Grand Caravan, Town and Country, Durango, Grand Cherokee; 2012-2013 Wrangler)
Warranty extension X56 (bulletin 09-002-14 REV. A, October 2014): P0300, P0302, P0304 or P0306 from the left cylinder head. Coverage is 10 years or 150,000 miles from the in-service date.
Chrysler 09-002-14 REV. A via NHTSA static.nhtsa.gov
-
Honda 2016-2017 Pilot, 2017 Ridgeline, 2018 Odyssey
Honda bulletin 20-100 (February 2021): worn fuel injectors can cause misfires on these V6 engines. It covers P0300 to P0306, and the fix is new injectors, for 10 years or 150,000 miles from purchase.
Honda 20-100 via NHTSA static.nhtsa.gov
Related codes
How Obie handles P0306
Obie reads the misfire counts per cylinder where your car reports them, walks you through the coil swap, and checks the counts again after the next drive. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Where is cylinder 6?
It depends on the engine. Your repair manual or an engine diagram for your exact engine shows it. Do not guess: the wrong cylinder means the wrong part.
Can I drive with P0306?
Gently for a few days with a steady light. Not with a flashing light.
Is P0306 the coil or the plug?
Swap the coil to another cylinder. If the misfire moves, it is the coil. If not, check the plug next.
Sources
- RepairPal: P0306 code page repairpal.com
- RepairPal: Engine compression test (updated September 3, 2026) repairpal.com
- RepairPal: Ignition coil replacement (updated September 3, 2026) repairpal.com
- RepairPal: Spark plug replacement (updated September 3, 2026) repairpal.com
- RepairPal: Fuel injector replacement (updated September 3, 2026) repairpal.com
- CarMD 2026 Vehicle Health Index (press release, April 22, 2026) prnewswire.com
- Chrysler 09-002-14 REV. A via NHTSA static.nhtsa.gov
- Honda 20-100 via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0306 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.