P0306 – Cylinder 6 -misfire detected
Last Updated 2017-08-26
ASE Master Tech
|Code||Fault Location||Probable Cause|
|P0306|| Cylinder 6 -misfire detected |
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|Engine mechanical fault, wiring, ignition/fuel system, injector, ECT/MAF sensor, ECM|
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Table of Contents
- What Does Code P0306 Mean?
- What are the common causes of code P0306 ?
- How do you troubleshoot code P0306 ?
- Get Help with P0306
What Does Code P0306 Mean?
A misfire is just what it sounds like; a cylinder that is not firing as it should. The P0306 code is caused by a misfire on the number six cylinder. The Misfire monitor diagnostic is based on variation in crankshaft velocity. The PCM determines this information using the crankshaft position sensor and camshaft position sensor. A misfiring cylinder slows down momentarily, so by monitoring the cam and crank sensor signals, the PCM can calculate when a misfire occurs. A P0306 code tells you only that a misfire has been detected, not WHY the cylinder is misfiring. That’s why with this code, a thorough diagnosis is mandatory.
Different manufacturers implement OBD-II requirements slightly differently. The misfire monitor is an OBD-II procedure which identifies a misfire.
The misfire monitor is a “continuous” monitor; it is always checking the crankshaft position sensor for a misfire. It is important to note that the misfire monitor is very reliant on the crankshaft position sensor signal. A faulty crankshaft position sensor will misdiagnose misfires!
What are the common causes of code P0306 ?
When you encounter a single cylinder misfire, the causes of systemic misfires such as: fuel pumps, timing problems, EGR valve leaks, or crankshaft position sensors are less likely. Individual spark plugs, fuel injectors and valves should be carefully examined for the cylinder. For companion cylinders, the cylinder noted by the PCM may test fine. Be sure to check its companion in the firing sequence. For a P0306 code, the causes could be:
- Cylinder #6 Spark Plug
- Cylinder #6 Coil
- Cylinder #6 Wiring
- Cylinder #6 Fuel Injector
TIP: Check for a technical service bulletin. There could be a known repair for a single cylinder code. Sometimes the PCM errors.
How do you troubleshoot code P0306 ?
Often, the best way to troubleshoot a single cylinder misfire is to swap ignition components between the misfiring cylinder and a good cylinder. If the misfire moves with the sparkplug (for example) then the sparkplug would be the cause of the misfire. If switching components to a good cylinder doesn’t eliminate the original misfire then there could be a problem with compression. See articles P0300 & P0301 for in depth troubleshooting of the four misfire causes: fuel, spark, timing, and compression.
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I have an 04 Buick park ave ultra and a misfire on cylinder 6 where should I start to try to fix, spark plugs?
Hello Danielle. Checking the spark plugs is a good preliminary check. When I have dealt with this issue, it has usually been a bad 3/6 coil pack. These Buicks have a waste spark design and frequently just one side of the coil will go bad.
I’ve replaced the coil pack and spark plug/wires still no luck, do you think it’s the fuel injector?
Thank you, I was going to try the plugs then coil pack and maybe if those don’t help them the ignition control module…
Will a 02 sensor and cylinder 6 make the car not run good. If you take your foot of the gas pedal it quites
i have 2004 grand marquis
cyclinder 6 keeps misfiring
I have replace spark plug, coil and injector several times.
I had my car hooked up to a scanner and about six different codes popped. I need help
What other codes were there? Is the car running poorly? Also, what vehicle?