OBD-II trouble code
P0311: Cylinder 11 Misfire Detected
Cylinder 11 is losing combustion events. Before touching a part, understand that the module never watched cylinder 11 burn — it watched the crankshaft slow down and worked backwards to a cylinder number.
Quick facts
- System
- Powertrain
- Category
- Ignition / Misfire
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $3,000
- DIY difficulty
- Advanced DIY
What does P0311 mean?
No engine controller has a sensor that looks inside a combustion chamber. What it has is a crankshaft position sensor counting teeth on a reluctor wheel thousands of times per second, and a very precise expectation of how much the crank should accelerate on each power stroke. When the acceleration for one stroke falls short repeatedly, the module converts a timing window into a cylinder number using the firing order stored in its calibration and the camshaft signal that tells it which half of the four-stroke cycle it is in. P0311 is the output of that conversion.
That matters more here than it does on a low-numbered cylinder. Attribution is only as good as the three things it depends on: an accurate crank reluctor, a valid cam-to-crank correlation, and a completed crankshaft variation learn. If any of those is off, the module can still count misfires correctly and still put the wrong number on them. So a lone high-numbered misfire code with no supporting evidence — no rough idle you can feel, no fuel trim movement, nothing on the tailpipe — deserves a moment of scepticism before an eleventh coil is ordered. Check whether P0315, P0335, P0336 or a camshaft correlation code is also stored. If one is, fix the attribution before you trust the attribution.
The second thing worth settling before any work begins is which bank cylinder 11 lives on. Only twelve-cylinder engines report it, and on a V12 the near-universal convention places odd-numbered cylinders on one bank and even-numbered on the other, or numbers each bank front-to-back in sequence — and manufacturers genuinely differ on which. Getting this wrong sends you to the wrong side of the engine, the wrong cam bank, the wrong fuel rail and the wrong set of long-term fuel trim numbers. One minute with the correct service information for that specific engine saves an afternoon.
Once attribution is trusted and the bank is known, P0311 is an ordinary misfire and yields to ordinary misfire logic. What is not ordinary is the cost of guessing on an engine with twelve of everything, which is why the diagnostic order below puts free evidence first.
Common causes
- Failed ignition coil on cylinder 11
- Spark plug at the end of its life, worn to a gap the coil can no longer bridge under load
- Clogged, leaking or electrically failed fuel injector on cylinder 11
- Intake or vacuum leak affecting the runner feeding cylinder 11
- Damaged coil connector or chafed harness branch on that cylinder
- Low compression from a burnt exhaust valve, worn rings or a head gasket breach
- Carbon deposits on the intake valve restricting airflow on direct-injection engines
- Misattribution caused by a crankshaft reluctor fault or an incomplete crank variation relearn
- Camshaft position correlation drift causing the module to assign the misfire to the wrong cylinder
Symptoms
- Check engine light flashing during the misfire, steady once it stops
- Rough or uneven idle
- Noticeable stumble under acceleration
- Reduced power and worse fuel consumption
- Exhaust note that sounds slightly uneven at idle
- Misfire counters climbing on one cylinder while the rest stay at zero
- In some cases no felt symptom at all, because eleven other cylinders mask one weak one
Diagnostic steps
- 1.Pull every stored code before doing anything else. A crank or cam position code stored alongside P0311 changes the job from repairing a cylinder to repairing the module's ability to identify a cylinder.
- 2.Confirm the cylinder numbering and bank assignment for this exact engine from manufacturer service information rather than from a generic diagram.
- 3.Look at the live misfire counters for all twelve cylinders, not just the one named. One counter climbing alone is a component; several climbing on one bank is a fuel or air supply issue on that bank; counters scattered across both banks means the real fault is global and P0311 is a symptom.
- 4.Record freeze frame before clearing anything. Engine speed, calculated load, coolant temperature and fuel trim at the moment the code set tell you which condition to reproduce, and a misfire that only appears at 2,000 rpm under load will never show itself at idle in a bay.
- 5.Check that the crankshaft variation relearn has actually been performed if the crank sensor, the balancer, the flexplate or the PCM has been touched in this vehicle's recent history.
- 6.Test ignition on the named cylinder — coil primary and secondary resistance where the manufacturer publishes it, or coil output on a scope — and inspect the connector for heat damage.
- 7.Only after ignition, fuelling and air have been eliminated should compression be measured, and compare cylinder 11 against the average of its own bank rather than against a book figure.
Repair cost
$150 – $3,000
Parts for a single cylinder are unremarkable — a coil is $80 to $300 and a plug is $15 to $60 — but almost nothing on a twelve-cylinder engine is a ten-minute job, and shops usually decline to replace one plug of twelve, so a plug job frequently arrives as a full set at $500 to $1,400 with labour. Injector replacement lands at $400 to $1,000. An intake or plenum gasket on the affected bank runs $500 to $1,500. If compression testing sends the job into the cylinder head, budget from $3,000 upward. Diagnostic time is the cheapest money you will spend on this code.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with ignition coil replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.