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P0301 is a diagnostic trouble code (DTC) for "Cylinder 1 Misfire Detected". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
Cylinder 1 misfire detected
There are 4-6 cylinders in most vehicles. In order, each cylinder fires a spark plug in a smooth and steady manner. The spark plug sets a fire to the fuel, using a flammable fuel/air mixture. The crankshaft is then powered by energy that is released by the fuel.
The cylinders control the revolutions per minute (RPM) of the crankshaft. All of the cylinders work together to ensure the continuous rotation of the crankshaft. If a cylinder misfires, the crankshaft revolutions per minute will increase or decrease.
If the powertrain control module detects that there is an increase or decrease of the crankshaft revolutions per minute that is more than 2 percent, it will store the P0301 trouble code.
The Check Engine Light will come on if the percentage of increase or decrease in crankshaft revolutions per minute is between 2 percent and 10 percent. The Check Engine Light will blink if the percentage of the increase or decrease in crankshaft revolutions per minute is more than 10 percent.
A percentage increase or decrease in revolutions per minute greater than 10 percent indicates that the misfiring problem is more serious. The P0301 trouble code indicates that cylinder 1 is not getting the necessary spark resulting in a misfiring condition.
Collects all trouble codes and freeze frame data stored by the powertrain control module, using an OBD-II scanner
Test drives the vehicle to see if the P0301 trouble code returns
Inspects the spark plug wire for cylinder 1 for damage or excessive wear
Inspects the spark plug cylinder itself for damage or excessive wear
Inspects the coil packs for damage or excessive wear
Inspects coil pack wires for damage or excessive wear
Replaces spark plugs, spark plug wires, coil packs, and coil pack wiring if needed
After replacing these components, if the P0301 trouble code returns, it may be necessary to inspect the fuel injectors and fuel injector wiring to see if they are in any way defective.
They will inspect the distributor cap and/or rotor button for corrosion and/or cracks (Older vehicles have a distributor cap and rotor button system - this step is not applicable to all vehicles).
Diagnoses and repairs any other codes that have been stored by the powertrain control module and are related to the P0301 trouble code.
Repeats a test drive to see if the P0301 trouble code returns.
After the test drive, if the P0301 trouble code returns, they will inspect the compression system of cylinder 1 (this is rare).
There could be an issue with the powertrain control module, if the P0301 trouble code persists. This is rare, but it may require replacing or reprogramming.
Before replacing the spark plugs, spark plug wires, coil packs, and coil pack wires, complete a visual inspection of the fuel injector wiring for damage.
Although it is rare for faulty fuel injectors to be the problem, completing a quick visual inspection could save some time. Make sure that the possibility of a faulty cylinder is ruled out as the cause of the problem.
It is also important to complete a diagnosis and necessary repairs of other related trouble codes, that have been stored by the powertrain control module. Any of these components could be the cause of the misfiring problem.
The P0301 trouble code is considered a serious one because of the drivability issues that exist when this trouble code has been stored by the powertrain control module. Driving may become hazardous and/or dangerous if the car randomly stalls or stops while the vehicle is being operated. The P0301 trouble code should be addressed as soon as possible.
One quick way to make a determination as to whether the misfiring problem is the result of a faulty wire or coil pack is to switch the wire and/or coil pack with another one. If a trouble code for a different cylinder comes back, this is a good indication that the wire and/or coil pack is causing the misfire.
It is important to replace all spark plugs when repairing any misfire trouble code. Only replacing the spark plug for the misfiring cylinder may result in other cylinders misfiring afterwards. If there are other related codes stored in the powertrain control module, be sure to inspect and diagnose those codes.
It is also important to make sure the spark plugs have been precisely gapped. Neglecting to do so will cause a misfire. The spark plugs should be gapped according to the the manufacturer’s specifications. These specifications can be located under the vehicle’s hood on a sticker. Any local auto part store will have the gap specifications as well. A feeler gauge will be necessary to gap the spark plugs properly.
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