What Does Chevrolet Code P0300 Mean?
- P0300 definition: Random, Multiple Misfire Detected
- Code Severity: SEVERE – Stop driving immediately
- Repair Urgency: Fix this trouble code immediately (same-day if possible) to avoid ignition failure, catalytic converter damage, and dangerous conditions
- Diagnosis: A multiple cylinder misfire can be caused by anything from faulty spark plugs to low engine compression. You can take your car into a shop for diagnosis, or click here to save money by fixing P0300 yourself with FIXD!
- One of the top 5 most common causes of a check engine light in 30 out of the 59 Chevrolet models we have data on.
Your Chevrolet vehicle moves when gasoline is burned and power is generated inside a chamber known as the cylinder. Most engines have a 4, 6, or 8-cylinder engine, where more cylinders typically mean more power. Power is generated by pistons that move up and down while fuel is ignited at very specific times. A cylinder misfire typically occurs when the timing of this ignition is off. P0300 indicates that there are two or more cylinder misfires. This is one of a few air-to-fuel ratio problems car owners will want to repair ASAP, misfires are bad regardless of how often the misfire occurs (misfire rate).
Chevrolet P0300 (Multiple Misfire Detected) – Causes
A “multiple misfires detected” code can be caused by a faulty ignition system, fuel system, or internal engine failure. The most common reason for P0300 is faulty or worn-out spark plug coil packs, especially if it’s been a while since you last had a tune-up.
- Faulty or worn spark plugs and/or spark plug wires
- Ignition issues, including failing or damaged ignition coils
- Distributor failure
- Faulty fuel injector
- Vacuum leak
- Low fuel pressure
- Camshaft and/or crankshaft sensor defective
- Engine timing off
- Leaking head gasket
- Low engine compression
- Poor quality fuel that is old or contaminated
Chevrolet P0300 Symptoms
- Check Engine Light is on or flashing
- Engine runs rough, hesitates, or jerks when accelerating
- Drivers may not notice any adverse conditions when driving
- In some cases, drivers may experience decreased fuel economy, fuel smell from exhaust, rough idling, or lack of power from the engine
- Commonly associated with error codes: P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308
How Do I Fix Chevrolet Code P0300 Check Engine Light (Engine Misfire)?
With a misfire detected trouble code, the first step is to figure out what is causing the engine misfire. We’ve created this 100% free step-by-step guide to show you how to diagnose and repair your Chevy’s P0300 code.
The FIXD Sensor and app can help you diagnose and repair a P0300 code yourself by giving you access to detailed engine diagnostics that are easy to understand (even if you don’t know cars), live OBD2 data, and a Mechanic Hotline. You can even use FIXD to clear the trouble codes on your Chevrolet and see if your repair worked, or simply turn off codes that aren’t serious.
> Click here to get FIXD for $19.99 for a limited time!
If your vehicle is misfiring and you’re not comfortable diagnosing this issue at home, we recommend finding a Repair Pal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs and service.
These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.
How Much Does It Cost to Fix an Engine Misfire?
P0300 can be caused by anything from old spark plugs to vacuum leaks to poor engine compression. Just like any other trouble code, it’s impossible to give an accurate estimate of repair without properly diagnosing the issue first.
If you take your vehicle to a shop for diagnosis service, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis service fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0300 code.
Remember, alway check for technical service bulletins like this one for the trouble code in question- Bulletin No.: 15-06-01-002I on Chevrolet P0300 issues to find common and documented problems. If your vehicle has one of these documented issues you may be able to get your repair done free of charge at a dealership.
Search “Service bulletin {OBDII Code} {Make} {Model}” on Google to find your particular model Ex: “service bulletin p0300 chevy tahoe”. A bulletin OBDII code titled or not, is a good place to start just to rule out the common culprits.
Possible Repair Costs for an Engine / Cylinder Misfire
Once properly diagnosed, code P0300 may require one or more of the following repairs to resolve the underlying issue. These prices are based on national averages and include parts and labor service. Your cost may differ depending on your location and type of vehicle.
- Spark plugs: $66-$250
- 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
DIY Steps to Diagnose Chevrolet Code P0300
Engine code P0300 could be caused by a number of things, including faulty spark plugs, faulty ignition system, distributor failure, and more. If you’d like to try to repair trouble code P0300 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis.
Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.
DIY difficulty level: Intermediate
This repair requires mechanical knowledge and is not recommended for beginners.
Tools/parts needed (our top picks from Amazon):
- Screwdrivers
- FIXD
- Digital multimeter
- 5/8in. Spark Plug Socket
- Ratchet, sockets, and extensions
- Fuel pressure gauge
- Compression tester
- Leakdown tester
- Spark plugs
- Spark plug wires
STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.
Use FIXD to scan your Chevrolet to verify the P0300 code is the only code present. If other codes are present, they must be addressed first.
STEP 2: CHECK FOR LOOSE CONNECTORS OR DAMAGED WIRING AT THE IGNITION COILS.
Look for loose engine ground wires as well. These can cause random misfire conditions. Tighten or connect where necessary.
STEP 3: CHECK THE CONDITION OF YOUR SPARK PLUGS, SPARK PLUG WIRES, AND IGNITION COILS.
Worn and old spark plugs, spark plug wires, and ignition coils are common causes of random misfires. Replacing worn and old parts is part of regular maintenance for any car and should be done if needed (hopefully proactively to avoid misfires). After replacing the faulty plugs, wires and or coils, recheck for misfires.
If you are apprehensive on doing this level of maintenance, it may be best to call a mechanic. Getting a broken spark plug out of an engine can be difficult and spark plugs can break off if they are really stuck (because they are really old) or are extracted improperly.
> How to replace spark plugs in 4 easy steps
> How to identify a fouled spark plug
> How to test spark plug wires
STEP 4: CHECK TO ENSURE YOUR ENGINE IS GETTING THE PROPER AMOUNT OF FUEL.
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.
- Check fuel injectors: Make sure 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
STEP 5: PERFORM ENGINE COMPRESSION AND LEAKDOWN TEST
If the ignition system and fuel system checks out, you may want to perform an engine compression test and leakdown test to see if there are any mechanical problems causing your misfire.
Common mechanical problems that can cause misfires:
- Leaking Head Gasket
- Broken valve spring
- Broken piston ring
- Worn valve guides
- Burned valve
- Timing chain or belt skipped tooth and engine is off time.
Common P0300 Diagnosis Mistakes
Loose fitting electrical connectors and broken or disconnected vacuum hoses are often overlooked. Oxygen sensor(s) are another common misdiagnosis for P0300.
Still Need Help Fixing Chevrolet Code P0300?
If you’ve followed the steps above and are still experiencing misfires or check engine code P0300, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a Repair Pal certified shop near you to get the right repairs and service at a fair price. Don’t have a FIXD Sensor yet? Click here to get yours for just $19.99, including a free 14-day trial of FIXD Premium!
Popular Engine Codes p0420 code p0172 code p00171 code p0128 code p0300 code p0456 code p0430 code p0442 code p0455 code p0113 code
Fixed It But The Check Engine Light Is Still On?
Check engine light sometimes need to be reset manually, check out our article:
How to Reset Your Check Engine Light | 4 Ways To Clear It (With or Without a Scanner)
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.
