Ignition and misfires code
P0306: Cylinder 6 misfire
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $30 | $120 |
| Labor: 0.4 to 1.2 hours × $125 to $175 an hour | $50 | $210 |
| Fees: shop supplies, disposal, diagnostics | $0 | $15 |
| Total, rounded | $80 | $350 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, ignition coil replacement (one coil). Which repair your car needs depends on a proper diagnosis.
The computer found that cylinder 6 is not burning its fuel on every turn. It tells by measuring how the crankshaft speeds up after each firing, and the push after cylinder 6 is weaker. On a V6 this is often the last cylinder in the firing layout.
- Safe to drive?
- Short trips only
- Most common cause
- Worn spark plug in cylinder 6
A steady light means short drives are okay; a flashing light means stop, because raw fuel can ruin the catalytic converter.
What you may notice
- Shaking, worse at idle
- Flashing check-engine light
- Hesitation when accelerating
- Often a stronger fuel smell
Common causes, most likely first
- Worn spark plug in cylinder 6
- Failing ignition coil on cylinder 6
- Clogged or weak fuel injector for that cylinder
- Vacuum leak near that cylinder
- Low compression from a valve or ring problem
Check this first
Look up where cylinder 6 sits on your engine, then ask the shop to swap its coil with a neighbor and clear the code. If the miss moves, replace the coil. If not, the plug, injector or a leak near cylinder 6 is next.
Other repairs that sometimes fix P0306
| Repair | Typical range, Boston |
|---|---|
| Spark plug replacement | $95 to $580 |
| Fuel injector replacement (one injector) | $180 to $910 |
| Vacuum leak repair | $100 to $530 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P0306 questions
How do I know which cylinder is number 6?
The location depends on the engine layout, so use a diagram for your make and model. On a lot of V6 engines it is the rear cylinder on the second bank, and sits behind the intake, so access can be tight.
Should I replace the plug or the coil?
Start with the plug if it is overdue, and use the coil swap to check the coil. Cylinder 6 is sometimes hard to reach, so doing the test first can save you a repeat labor charge for the same spot.
Can I keep driving with this code?
A brief, easy drive is normally fine while the light is steady. Avoid towing or hard acceleration, and pull over if the light starts flashing, since the converter can overheat from unburned fuel.
How much does it cost to fix P0306?
The most common fix, ignition coil replacement (one coil), has a typical range of $80 to $350 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
More ignition and misfires codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.