P0306 on Honda
Cylinder 6 Misfire Detected
P0306 on Honda vehicles indicates cylinder 6 misfire detected. Au7o has documented this code across 4 Honda models — most commonly on Accord, Passport, Pilot. This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. Typical repair costs on Honda range from $81 to $8,000, depending on the specific model and root cause.
Common Causes of P0306
- •Worn or fouled spark plug on cylinder 6
- •Failed ignition coil for cylinder 6
- •Clogged, leaking, or failed fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt valve, head gasket)
- •Damaged plug wire or coil connector
- •Carbon buildup or worn valvetrain components
P0306 on Honda by Model
Honda Accord(1 issue)
- V6 VCM Excessive Oil Consumption and Engine Vibration2008-2012
The 8th generation Accord V6 (3.5L J35Z2) with Variable Cylinder Management (VCM) deactivates 3 cylinders at highway speeds, causing excessive oil consumption (1 quart per 1,000-1,500 miles), misfires, and accelerated engine vibration that damages engine mounts. When VCM deactivates cylinders, insufficient ring pressure allows oil to bypass rings into combustion chamber. The class action lawsuit (Rodriguez v. American Honda, 2013) covered 1.87 million vehicles. Honda settled in 2016 providing extended warranty for engine repairs related to VCM-caused misfires and oil consumption. Many owners in the Drive Accord community disable VCM immediately upon purchase.
Honda Passport(2 issues)
- Timing Belt and Water Pump Neglect Leading to 3.2L V6 Engine Damage2000-2002
The 3.2L V6 used in the first-generation Passport relies on a timing belt service interval that many used examples miss. When the belt, tensioner, or water pump fails, owners report sudden no-starts, stalling, or catastrophic internal engine damage because the engine is interference-design. Forum history and repair databases repeatedly flag overdue timing-belt service as one of the most important reliability risks on these trucks.
- Valve Cover Gasket and Spark Plug Tube Seal Oil Leaks Causing Misfires2000-2002
Aging 3.2L V6 Passports commonly develop oil leaks from the valve cover gaskets and spark plug tube seals. Owners report burnt-oil smell, oil on the cylinder head, and in some cases oil filling the plug wells and causing ignition misfires. This is a typical age-related failure on the Isuzu-sourced V6 and becomes more common as rubber seals harden with heat.
Honda Pilot(3 issues)
- VCM System Causes Excessive Oil Consumption and Misfires2016-2022
Variable Cylinder Management (VCM) causes excessive oil consumption (1 quart every 1,000-1,500 miles), engine misfires, and fouled spark plugs. The reciprocating effect creates vacuum that pulls oil past piston rings. Leads to premature failure of spark plugs, catalytic converters, engine mounts, and cylinder walls. 2013 class action lawsuit identified 1.6 million affected vehicles.
- Fuel Injector Debris Causing Misfires and Catalyst Codes2016-2018
2016-2018 Pilots suffer from debris in direct-injection fuel system causing internal wear or clogging inside injectors. Causes misfire codes (P0300-P0306), catalyst efficiency codes (P219A/B, P0420/P0430), rough idle, and stalling. TSB 20-100 addresses this defect. Honda extended warranty to 10 years/150,000 miles for 2016-2017 models.
- Valve Cover Gasket and Spark Plug Tube Seal Oil Leak Causing Misfires2009-2020
On the J35 V6, the rubber valve cover gaskets and the integrated spark plug tube seals harden and shrink with age and heat, allowing oil to weep onto the hot exhaust manifolds (burning-oil smell) and, more seriously, to pool down inside the spark plug wells. Oil saturates the ignition coil boots and shorts the spark, producing misfires and a Check Engine Light. The rear (firewall-side) bank is hardest to access, so the leak is often neglected until misfires appear.
Honda Ridgeline(3 issues)
- VCM System - Excessive Oil Consumption and Misfires2006-2014
Variable Cylinder Management (VCM) deactivates 3 cylinders during light-load driving to improve fuel economy. When inactive cylinders reactivate, vacuum pulls oil past piston rings into the combustion chamber, causing excessive oil consumption (1 quart per 1,000-1,500 miles vs. normal 1 quart per 3,000-5,000). Oil burning causes spark plug fouling, misfires, rough idle, and accelerated catalytic converter wear. 2013 class action lawsuit identified 1.6 million affected Honda vehicles including 2006-2013 Ridgelines.
- Spark Plugs Backing Out - Coil Pack Melting and Engine Damage2006-2010
The 3.5L aluminum engine with steel spark plugs experiences thermal stress due to temperature differences. Spark plugs back out (loosen) due to aluminum block expansion/contraction cycles, causing misfires and potentially breaking inside the combustion chamber. Loose spark plugs allow coil packs to melt and enter the engine block causing catastrophic damage. After 60,000 miles, Honda service bulletins specify spark plug torque should be double-checked. Affects all J35 engine platforms (Pilot, Odyssey, Ridgeline).
- Hydraulic Timing Belt Tensioner Leaks Down - Belt Skip and Interference Engine Damage (J35A9)2006-2014
The 2006-2014 Ridgeline's J35A9 uses a belt-driven cam system with a hydraulic (oil-filled) timing belt tensioner rather than a spring tensioner. The tensioner seal weeps, the damper loses its charge, and belt tension goes slack. Ridgeline Owners Club threads report technicians finding a large share of high-mileage tensioners leaking. A slack belt lets the belt jump a tooth on a cam sprocket - first showing up as a random misfire under load - and if it skips far enough or shears, the J35 is an interference design and bends valves. The water pump is driven off the same belt and is a common co-failure, so a leaking tensioner discovered late often means the whole front of the engine.
Looking for P0306 on a different make?
View P0306 across all makes →Frequently Asked Questions
What does P0306 mean on Honda?▼
P0306 stands for "Cylinder 6 Misfire Detected." This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. On Honda specifically, this code is documented across 4 models.
What causes P0306 on Honda vehicles?▼
Common causes on Honda: Worn or fouled spark plug on cylinder 6, Failed ignition coil for cylinder 6, Clogged, leaking, or failed fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0306 on a Honda?▼
Repair costs on Honda range from $81 to $8,000, depending on the specific model and root cause.
Which Honda models have P0306 documented?▼
Au7o has documented P0306 on 4 Honda models: Accord, Passport, Pilot, Ridgeline.