OBD-II Code P0306? (Cylinder 6 Misfire Detected)

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How to fix the P0306 obd2 code
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According to the P0306 code, a misfire in cylinder 6 occurs. A four- or six-cylinder engine powers the vast majority of automobiles. Many trucks will also be equipped with a six- to eight-cylinder engine.

The P0306 error code can appear in motors with six or more cylinders. Cylinder 6 misfire refers to the fact that it will only affect cylinder 6. A misfire happens when the engine’s cycle breaks. The engine may buck due to skipping a step in the operating cycle.

P0306 Code Meaning

P0306 Code Meaning

P0306 is an OBD2 generic code. The engine’s central controller detects misfires in cylinder 6. Fuel combustion efficiency is critical in engine performance. Fuel combustion is required to generate energy for the engine to run. A misfire can occur if there is a problem with the fuel supply or an insufficient amount of fuel.

OBD-II Code P0306: Symptoms, Causes & Diagnose


When an engine misfires, you’ll notice several symptoms in your vehicle.

  • To begin, the Check Engine Light will illuminate. The code will be saved in the engine control unit’s memory. In a cylinder six misfire, the Check Engine Light will also blink.
  • It’s possible that a car will buck if it has P0306 engine misfires. When the vehicle is accelerating or idle, this frequently happens. The vehicle will feel shaky or unsteady if the engine misfires.
  • You may also notice a reduction in engine efficiency. The absence of engine power may affect transmission movement. It is possible for an effective cylinder with 6 misfires to occur during acceleration.


  • The starter motor for cylinder 6 is not firing due to corrosion or breaks in the insulator.
  • Cylinder 6’s igniter has stopped firing due to damaged insulation or an open circuit.
  • The ignition system wire or plug boot for cylinder 6 loses ignition spark to the ground due to its condition.
  • The valve cover leaks oil into the spark plug holes, causing the ignition of the 6 cylinder to be shorted.
  • The cylinder’s compression is low due to faulty rings or valves.

How to diagnose obd2 code P0305

Inspect your vehicle with FIXD to check that P0306 will be the only code present. If there are any other codes, these must be addressed first.

Examine the ignition coils for loosened connectors or faulty wiring (specifically cylinder 6). Look for dangling engine grounded wires as well. This can result in intermittent misfires. Tighten or adjust as needed.

Common mistakes you must avoid when diagnosis P0306

There are a few common mistakes to avoid when diagnosing the P0306 code.

  • The coil was not moved to a different cylinder to see if the misfire spread. This is an indication of a faulty coil.
  • To isolate the faulty portion, do not replace one cylinder at a time.
  • Loose or detached electrical connectors, and vacuum hoses that are broken or disconnected, are frequently overlooked.

How to fix P0306 Obd2 Code

How to fix

Examine the condition of spark plugs and its wires. Simply remove the cylinder 6 coil and replace it along with the cylinder four coils if your car has individual coil packs rather than spark plug wires. If the misfire has advanced to cylinder 4 (P0304), the coil pack is broken and must be replaced.

You can do the same thing with the spark plugs by moving the cylinder 6 plugs too, say, cylinder three, and see if the misfire code is now P0303, indicating that the plugs are faulty. As needed, change the spark plugs, spark plug wires, and ignition coil packs, and recheck for misfires. (How to determine if a spark plug is clogged.) Look for how should spark plug wires be tested? 

How to Change Spark Plugs, Gap Spark Plugs, and Swap Ignition Coils

If you’ve verified that your ignition system is in good operating order, the odd misfires could result from a fuel system malfunction. Check the following to assure that the engine receives the right amount of gasoline: It is necessary to check the fuel pressure. Multiple cylinders to misfire intermittently can be caused by low fuel pressure. When the pressure drops below the acceptable level, the engine obtains inadequate gasoline and starts misfiring. The fuel pump or the fuel pressure controller could be blamed for low fuel pressure. (Learn how to test your fuel pressure.)

Check to verify if the fuel injectors are turning on and working properly. Misfires that occur at random can indicate that the fuel injectors are defective or clogged and must be changed. In addition, make certain that the fuel injector wire is not harmed and is correctly connected. (How to test fuel injectors with a digital multimeter, How to test fuel injectors by ear)

Suppose the ignition and fuel systems are both operational, run an engine compression and leak-down test to rule out any mechanical problems that could be causing the misfire. Misfire can be caused by several mechanical issues, such as:

  • The head gasket is leaking.
  • Valve spring that has snapped
  • A piston ring has snapped.
  • Valve guides that have deteriorated
  • a smoldering control valve
  • The engine is out of sync because the timing chain or belt has skipped a tooth.

Tools you need to process

You may already have the following tools:

  • Screwdrivers
  • The multimeter (digital)
  • 5/8in. Spark Plug Socket
  • Ratchets, extensions, and sockets
  • Gasoline pressure gauge
  • Compression tester
  • Leak detector
  • The ignition system’s plugs
  • Spark plug wires

How serious is the P0352 code?

  • A misfiring cylinder may cause the engine to run too richly, damaging the catalyst.
  • As a result of the misfire, the engine will run rough and stutter under acceleration.
  • The engine will use more fuel as a result of the misfire.  P0352

What solutions are there for the P0306 error code?

  • Replace the spark plug or all spark plugs as a set if a worn-out spark plug caused the failure.
  • The failed coil, plug wires, and plugs should be replaced first, followed by the leaky valve cover gasket.
  • If a faulty circuit powers the fuel injector or coil, replace the ECM.
  • For your consideration, here are some additional comments on the P0306 code.
  • When the crankshaft sensor does not receive proper acceleration from cylinder number 6, code P0306 is set, indicating that the cylinder is not contributing to engine power.


The P0306 code is displayed when a serious problem with cylinder 6 misfiring. It may cause engine damage and should be repaired as soon as possible.