P0300 OBD-II Trouble Code: Random/Multiple Cylinder Misfire Detected

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0300 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0300 code

P0300 is a diagnostic trouble code (DTC) for "Random/Multiple Cylinder 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 for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$70.00$30.00
Toyota$70.00$30.00
BMW$70.00$30.00
SCHEDULE P0300 DIAGNOSTIC Get a fair and transparent estimate upfront

Check Engine Light

P0300 code definition

Random/multiple cylinder misfire detected

What the P0300 code means

Most vehicles will have 4-6 cylinders. Each cylinder will fire a spark plug, one after another, in a smooth and continuous manner. The spark plug fires a spark, using the flammable fuel air mixture, and sets fire to the fuel. The fuel then releases energy that powers the crankshaft, which must continuously turn smoothly as the car is moving.

If more than one cylinder misfires, this will increase or decrease the revolutions per minute (RPM) of the crankshaft. If that increase and/or decrease is more than 2 percent, the Powertrain Control Module will store the P0300 trouble code.

If the percentage of the increase or decrease in revolutions per minute (RPM) is between 2 percent and 10 percent, the Check Engine Light will come on. If the percentage of the increase or decrease in revolutions per minute (RPM) is greater than 10 percent, the Check Engine Light will blink on and off, as to alert the driver of a more serious misfiring problem. The P0300 trouble code indicates that there is a misfire in random or multiple cylinders.

What causes the P0300 code?

  • Spark plugs that are damaged or worn
  • Spark plug wires and/or coils that are damaged or worn
  • Distributor cap that is damaged or worn (only if applicable to the vehicle)
  • Rotor button that is damaged or worn (only if applicable to the vehicle)
  • Fuel injectors that are defective
  • EGR valves or tubes that are clogged
  • Ignition timing that is off
  • Vaccum leaks
  • Fuel pressure that is low
  • Head gasket(s) that are leaking
  • Distributor cap that is cracked
  • Camshaft sensor that is faulty
  • Crankshaft sensor that is faulty
  • Mass air flow sensor that is faulty
  • Oxygen sensor that is faulty
  • Throttle position sensor that is faulty
  • Catalytic converter that is faulty
  • PCM is faulty

What are the symptoms of the P0300 code?

  • Check Engine Light that is on or flashing
  • Car may take longer to start up, or does not start up at all
  • Car dies while stopped
  • Car idles rough
  • Car may hesitate while accelerating
  • Lack of power while driving
  • Increase of fuel consumption

How does a mechanic diagnose the P0300 code?

  • Uses OBD-II scanner to retrieve freeze frame data and all of the trouble codes that have been stored by the Primary Control Module (PCM)

  • Completes a test drive of the vehicle to see if the P0300 trouble code comes back

  • Reviews live data to identify which cylinders are showing misfire data

  • Inspects spark plug wires or coil packs for wiring that is damaged or worn

  • Inspects spark plugs for excessive wear, cracks, or breaks

  • Inspects coil pack wiring at the harness and connector, for breaks, or corrosion

  • Replaces spark plugs, spark plug wires, coil packs, coil pack wiring at harness and connector, as necessary

  • If the P0300 trouble code is still present after the spark plugs, spark plug wires and/or coil packs have been replaced, they will inspect the fuel injectors and fuel injector system for faults

  • Older vehicles have a distributor cap and rotor button system. For these vehicles, the mechanic will inspect the distributor cap and rotor button for damage, cracks, or excessive wear

  • If other related trouble codes have been stored by the PCM, the mechanic will need to diagnose and repair these issues as necessary. Test drive the vehicle again to see if the P0300 trouble code comes back.

  • If the P0300 trouble code returns, the compression system should be checked. A fault in the compressor is rare but possible for this code.

  • If the P0300 trouble code still persists, there could be a problem with the PCM. This may require replacing or reprogramming. This is also rare.

Common mistakes when diagnosing the P0300 code

One common mistake is ruling out the possibility of a faulty cylinder, fuel injector, or PCM. It is also common that the diagnosis and repair of other related trouble codes, is not completed.

Other related trouble codes, a faulty cylinder, a faulty fuel injector(s), and/or a faulty PCM can all cause the misfiring problem.

How serious is the P0300 code?

The P0300 trouble code is considered serious. The reason for this is the resulting driveability problems that are present when this trouble code is stored in the PCM. The car may not start and/or cause hazardous conditions during the operation of the vehicle. For these reasons, the P0300 trouble code requires immediate attention.

What repairs can fix the P0300 code?

Additional comments for consideration regarding the P0300 code

Do not assume that the spark plugs and wires are responsible for the P0300 trouble code. There are other components of the system that could cause this error code that should be diagnosed and inspected prior to repair.

Also, there are other related trouble codes that could cause the P0300. After repairs, if the P0300 trouble code returns, inspect and diagnose these other trouble codes if applicable. Always test drive the vehicle to see if the P0300 trouble code returns after making any repairs.

Make sure the spark plugs are gapped properly and with precision. To gap the spark plugs properly, it will be necessary to use a feeler gauge.

If the spark plug gap is not precise, this will cause a misfire.The vehicle manufacturer provides the spark plug gap specifications. These specifications can be found on a sticker under the hood of the vehicle or obtained from any local part store.

Need help with a P0300 code?

YourMechanic offers certified mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

P0300
Check Engine Light
trouble codes

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0300 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.5/5

Number of Reviews

3,788

Rating Summary
3,460
163
43
24
98
3,460
163
43
24
98

Russell

24 years of experience
152 reviews
Russell
24 years of experience
Russell is very knowledgeable, skilled and thorough. He went above and beyond during the visit. Not only did he clear the checklight, he also provided a meticulous engine inspection along with friendly recomnendations for upcoming engine needs. In fact, when the problem later returned, Russell gave prompt and expert guidance to help resolve it. I would highly recommend Russell for your service needs.
1995 NISSAN SENTRA - CHECK ENGINE LIGHT IS ON - CASTRO VALLEY, CALIFORNIA

Peter

40 years of experience
1059 reviews
Peter
40 years of experience
Peter is very professional,courteous and punctual. My first time using this service and will definitely be using again.
2004 NISSAN MURANO - CHECK ENGINE LIGHT IS ON - LAVEEN, ARIZONA

Emmette

33 years of experience
269 reviews
Emmette
33 years of experience
Mechanic arrived 15mins before time. Explained and answered all my questions.
2017 CHEVROLET MALIBU - CHECK ENGINE LIGHT IS ON INSPECTION - WOODBRIDGE, VIRGINIA

Joseph

24 years of experience
351 reviews
Joseph
24 years of experience
Very knowledgeable.
2006 SAAB 9-7X - CHECK ENGINE LIGHT IS ON - HOUSTON, TEXAS

More related articles

How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It...
How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...

Related questions

Q: Barely any power when I step on the gas pedal, any ideas?

Hello. From the symptoms you describe it would appear that your vehicle is experiencing an issue that is putting it into some sort of limp mode. Limp mode is activated when the computer detects an issue that could potentially damage...

Q: Q: Car starts and then turns off

I would recommend starting with having your vehicle checked for trouble codes with an OBD2 scanner. Once the codes have been pulled by a knowledgable technician, a strategic diagnosis plan can be made. The Check Engine Light code will aid...

Q: New battery & fuel pump. Hours later car starts and shuts down 3X in a row. Finally it starts, 48 hours later, won't start at all

Checking all the fuses was a good move. I would also want to put a scan tool on it and check for diagnostic trouble codes (DTCs) as well as seeing the data that the computer is seeing. A fuel pressure...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com