Are you struggling with check engine light code P0301? Learn what causes this fault code and how to fix it with advice from an experienced mechanic.
Troubleshooting code P0301 (and other P030X codes such as P0302, P0303 etc.) is easier than most would expect because your vehicle's computer has already figured out which cylinder that is having problem... saving you a lot of diagnostic headache.
Misfire codes (P0302, P0303, etc.) are some of the most common OBD codes. They basically mean that there is a misfire on that respective cylinder in the firing order. For example, P0306 means "misfire cylinder 6", P0302 means "misfire cylinder 2" and so on.
If your car has one of these codes you need to get it fixed asap. If you choose to drive your car in this condition you will do damage to the catalytic converter.
Driving with a misfire causes unburned fuel to be put into the exhaust (because there is one or more cylinders that are not burning it like they should) which then is sent to the catalytic converter. It is not made to clean up exhaust with unburned fuel in it and will soon become faulty. This is an expensive repair so the best thing is just to get your car repaired! Let's see what are common causes and fixes for this trouble code:
To troubleshoot, repair and maintain your vehicle, you'll need diagnostic and repair information that is specific to your car or truck. For this I personally use and recommend ALLDATAdiy. With full manuals for over 30,000 vehicles online, you will find an exact match for your vehicle's year, make and model.
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The first thing to do if you have this code is to inspect EVERYTHING that has to do with that specific cylinder. Since the misfire code is for that cylinder only it has to be only something that would affect that cylinder and not the others. This is the key to diagnosing this problem.
You want to be looking at the spark plug, wire, coil and injector of that cylinder. You also perform a compression test with a compression tester kit... followed by a leak down test using a leak down tester to see if your piston rings or cylinder head valves are getting worn and causing low compression.
A good way to check the plugs, wires and fuel injectors is to switch them with different cylinders to see if the misfire moves with them.
Some of the easiest ways to diagnose this OBD code are to change parts. In order to figure out if the check engine light code P0301 (misfire on cylinder 1) is being caused by a fuel injector, you can (in most cases) just switch it with a different cylinder.
So if you switch the fuel injector from cylinder #1 (because of code 0301) with cylinder #3 you can then start the vehicle and let it run. When the check engine light comes back on you just read the codes again. If the code that comes back is p0303 then you know that the problem is the injector and you need a new one.
This method works for lots of things. You can use it with spark plug wires, ignition coils (assuming you have a coil for each cylinder), spark plugs, etc. If you have a coil on plug system (COP) then you can just switch the whole assembly with another one. This diagnosis method works for any P0xxx code.
Remember this type of code is one that cannot wait long for
you to attend to. You will likely notice lower fuel mileage, loss of
engine power, blinking check engine light and probably others too. Since
there is a misfire, that means that raw fuel is going into your
catalytic converter. The CAT is not made to process raw fuel. It will
not take long for the CAT to go bad and if it does you are looking at a
min. $500 repair bill.
If you still have any unresolved vehicle problems or questions, you can ask an auto mechanic online. For expert answers specific to your vehicle's make and model, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee and you can also browse their answers to other users for free.
Recommended Tools for Diagnosing and Fixing OBD II Codes
OBD II Scanner: Autel MaxiScan MS300 CAN Diagnostic Scan Tool
Combustion Leak Tester: UView 560000 Combustion Leak Tester
Compression Tester: Innova 3612 Compression Tester
Fuel Pressure Tester: Actron CP7838 Professional Fuel Pressure Tester
Leak Down Tester: OTC 5609 Cylinder Leakage Tester Kit
VEHICLE TROUBLE CODES
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