Ignition Systems ControlOBD2 Codes

P0305 – Meaning, Causes, Symptoms, & Fixes

P0305 cylinder 5 misfire detected

Code P0305 Definition

Cylinder 5 misfire detected.

Commonly associated with codes: P0300

What Does P0305 Mean?

P0305 indicates that cylinder number 5 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 P0305 occurs, it should be fixed immediately as long term driving with engine misfires could cause consequential damage to your engine.  Many times, P0305 occurs when there are worn-out spark plugs, spark plug wires, or a faulty ignition coil.

What Are The Symptoms Of Code P0305?

  • 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 P0305?

(* = 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 P0305? – Severe

P0305 should be repaired immediately. Ignoring this error could result in ignition failure, catalytic converter damage, and unsafe/dangerous conditions while operating the vehicle.

Code P0305 Common Diagnosis Mistakes

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

Tools Needed to Diagnose:

How To Diagnose P0305

Difficulty of Diagnosis and Repair – 2 out of 5

  1. Use FIXD to scan your vehicle to verify P0305 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 5). 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 5 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 5 plug to 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:
  5. 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)
  6. 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 to make sure 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)
  7. 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:
    • 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.

Estimated Cost of Repair

For error code P0305, 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

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22 Comments

  1. I thought i was just buying a code reader but in reality im getting expert advice that saves me even more money.

    1. All info made sense and lead me down the rite path!

  2. Expert advice and saved me a lot of time and money especially when dealing with a hobby vehicle

  3. Best investment I made in years. Wow, this unit and the support is incredible. Keep up the great advice, it had helped me out tremendously. Thanks so much for putting a tool out there that actually works better than advertised plus the bonus support.

  4. Fixd good stuff glad I purchased this product thank you and would recommend to any one

    1. Thanks John! So glad we could help!

      FIXD Team

  5. thank you guys very much good advice i needed to know

  6. I have a cylinder 5 misfire in a 98 Toyota Camry I have replaced the plugs wires crankshaft position sensor coil packs and it just keeps coming right back what could cause this

    1. I’ve changed plugs and coil and injectors are working but still having miss fire on c5.

      1. Did you ever figure out what your problem was, I too have changed the plugs, coils and injectors, don’t compression check but still having miss fire on number 5

  7. FIXD is an automotive education in a tiny package. Thank you for saving me headaches when the “check engine” light comes on in my Acadia.

  8. MISS FIRE CYL #5 My 1996 Toyota needed spark plugs as old plugs had 34K miles. Replaced plugs but still had miss fire on Cyl #5. Toyota 23 yrs old, 182K miles still with original “Ignition Coil on Spark Plugs”. Purchased new “Ign Coil on Plug”, problem solved.

  9. thank you you help me a lot !

    1. I have a misfire on cylinder 5 on my 2001 Ford explorer. I have replaced the plugs, wires, coil and have changed out the fuel filter. I can’t figure out what else would cause it to keep coming back on.

      1. check ur temp sensor..

  10. on my 2004 chevy blazer when i got the po305 code cyl 5 mis fire .. i thought like everyone else great tune up time.. but just did this yr before what could it be??? more digging lead me to the temp sensor right above the cyl 5 dummy test it the next day unpluging it an starting it up on a cold start it dint jump jurk like it was on the first start for the first 5min or so .. changed out the temp sensor runs great getting better gas mile now.. some times it pays off to dig alil to find the heart of the prob. js..

  11. Thanks, cylinder 5 keeps failing on mine too, this is the 5th or so time in 4 years. We are fixing the coil packs now and flogging it. Had enough, I love my car but sick of the repairs. This post has helped heaps

  12. Just made a comment about not knowing once I drop car off at repair shop..until I just watched the video on how to check before taking to the shop! With step by step instructions..OK..FIXD is ultimately awesome!!

    1. Thank you so much, Angela! We appreciate the kind words. Happy and safe driving to you and yours! 🙂

  13. Got the P305 code on my 2007 Honda Pilot with 154,334 miles on original engine. Changed out the spark plugs and coil packs but still getting the same code reading after that! What else should I check?

  14. Just bought your Fixd sensor. Watched your video too. Will ask my son to switch the coils on 5 to 4, since problems seems to be #5 cylinder. Hope that helps me out. We’ll see but video was very informative for me.

    1. Awesome to hear, Barbara! We are so glad your son will be able to help you make a quick, affordable repair. Thank you so much for using FIXD! 🙂

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