P0301 – Meaning, Causes, Symptoms, & Fixes

Code P0301 Definition

Cylinder 1 misfire detected.

  • Commonly associated with codes: P0300

What Does P0301 Mean?

P0301 indicates that cylinder number 1 is experiencing misfires. A misfire occurs when an insufficient amount of fuel is burning in a cylinder. The efficient burning of fuel is essential to engine operation as the combustion of fuel is what provides the energy to power the engine. A misfire from one or more cylinders can be caused by many reasons from a faulty ignition system, fuel system, or internal engine failure. When P0301 occurs, it should be fixed immediately as long term driving with engine misfires could cause consequential damage to your engine.  Many times, P0301 occurs when there are worn-out spark plugs, spark plug wires, or a faulty ignition coil.

What Are the Symptoms of Code P0301?

  • Check Engine Light is on
  • Check Engine Light flashing
  • Engine runs rough and shaking
  • Lack of power from the engine
  • Fuel smell from the exhaust
  • Hesitations/Jerking when accelerating

What Is the Cause of Code P0301?

(* = Most Common)

  • Faulty or worn spark plugs *
  • Faulty spark plug wires or coils *
  • Distributor failure *
  • Faulty fuel injector 
  • Vacuum leak
  • Low fuel pressure
  • Camshaft sensor defective
  • Crankshaft sensor defective
  • Engine timing off
  • Leaking head gasket
  • Low engine compression
  • Poor quality fuel

How Serious is Code P0301? – Severe 

 

P0301 should be repaired immediately. Ignoring this error could result in ignition failure, catalytic converter damage, and unsafe/dangerous conditions while operating the vehicle.

Code P0301 Common Diagnosis Mistakes

Loose-fitting electrical connectors and broken or disconnected vacuum hoses are often overlooked.

Tools Needed to Diagnose:

How To Diagnose P0301

Difficulty of Diagnosis and Repair – 2 out of 5

  1. Use FIXD to scan your vehicle to verify P0301 is the only code present. If other codes are present, they must be addressed first.
  2. Check for loose connectors at the ignition coils or for damaged wiring (specifically cylinder 1). Look for loose engine ground wires as well. These can cause random misfire conditions. Tighten or connect where necessary.
  3. Check the condition of your spark plugs and spark plug wires. If your vehicle is equipped with individual coil packs instead of spark plug wires, start by removing the cylinder 1 coil and swapping it with the cylinder number 4 coil. If the misfire moved to cylinder number 4 (P0304), then you have determined that the coil pack is faulty and needs replacement. You can do the same test with the spark plug, i.e., move cylinder 1 plug to say cylinder 3 and if the misfire is now P0303 then the plugs are at fault. Replace spark plugs and spark plug wires/ignition coil packs if needed and recheck for misfires. (How to identify a fouled spark plug, How to test spark plug wires, How to gap spark plugs, How to replace spark plugs, How to swap ignition coils)
  4. If you have determined that your ignition system is operating correctly, there may be a problem within your fuel system that is causing the random misfires. The following should be checked to ensure the engine is getting the proper amount of fuel: Check fuel pressure. Low fuel pressure can cause intermittent misfires on multiple cylinders. When the pressure is below the specification, the engine does not receive the proper amount of fuel and will start to lean misfire. The fuel pump or fuel pressure regulator could be the source of the low fuel pressure. (How to check fuel pressure). Check that the fuel injectors are functioning properly and activating. Random misfires can be a sign of faulty or clogged fuel injectors that need to be replaced. Also, check that the fuel injector wiring is not damaged and is connected properly. (How to check fuel injectors by ear, How to check fuel injectors with a digital multimeter)
  5. If the ignition system and fuel system checks out, you may want to perform an engine compression test and leak down test to see if there are any mechanical problems causing your misfire. Some common mechanical problems that cause misfire can be:
    1. Leaking head gasket
    2. Broken valve spring
    3. Broken piston ring
    4. Worn valve guides
    5. Burned valve
    6. Timing chain or belt skipped tooth and engine is off time.

Estimated Cost of Repair

For error code P0301, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Spark plugs $40-$640 (some cars require Intake manifold removal)
  • Ignition Coils $230-$640 (some cars require Intake manifold removal)
  • Spark plug wires $180-$240
  • Fuel injectors $1500-$1900
  • Vacuum leak $100-$200
  • Fuel pump $1300-$1700
  • Fuel pressure regulator $200-$400

Was this post helpful?

Comments 9

Sylvan Scott

August 4, 2018

Thanks! CEL came on, and the truck was idling loud and losing power. Switched out the spark plug and it’s running like butter.

Geoffrey Jones

November 12, 2018

Accidently over rev’ed the engine when I started it. Immediately got a flashing CEL with audible alarm. Engine ran rough when at idle speed. Checked the diagnostics using FIXD and gave me a code indicating cylinder #1 was misfiring. On the road, at about 40 mph, the engine ran very rough and seemed to be losing power. Most likely I will have to take it to the Dodge dealer ASAP to get all problems associated with over rev resolved. Unfortunately, I think it’s more than just a bad spark plug this time.

Devil

December 21, 2018

And what did u find my friend ? Because I had the same problem before an hour ago , but the CEL gone and everything went so fine , it only flashed for 4 seconds .

leonard geraci

December 19, 2018

The rough shaking and and idel only happens on startup. After that it run smooth and never misses at high speeds

Dana clark

January 15, 2019

I just had the plugs and all the gaskets changed, as well as all fluids flushed and replaced, ran diagnostics
With fixed module, and it the up a p0301 code came up! The people that did the work told me BMW requires a “special” diagnostic equipment, THAT IS BULL#$@&!
THEY WANT ME TO BRING IT BACK IN, NOT THIS LIFETIME! lesson learned

Shanta

February 6, 2019

I have the same problem! Code P301 came up meaning Cylinder 1. I have a 2005 Impala. This my second time changing out that same spark plug. The first spark plug I bought had broke off in there. And my mechanic got it out and put another one in. Now my car misfiring again and the same code popping up. What else could be wrong? Someone please help me!! Thanks!!

rigo

September 16, 2019

My code went away, should I still change my coil packs and spark plugs or just wait till it pops up again?

Undead

September 18, 2019

I would go ahead i had the same p0301 code pop up and it was a misfire on the coil pack

Patrick

September 24, 2019

As I was getting on the interstate I put my foot on the gas pretty hard to try and build speed while merging and I was at around 75 to 85 mph. At that speed I had to hit the gas hard again raising my rpms really high and before I could get out of the way of a truck the check engine light came on for about a mile down the road then went off. Trying to figure out if I should worry about my engine since it was this code that I’m getting.

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