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P0303 Toyota Code - Cylinder 3 Misfire Detected

Quick Answer

When the engine misfires, high concentrations of Hydrocarbons (HC) enter the exhaust gas. Common causes include Intake air leak, Faulty spark plug #3, Faulty ignition coil #3. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0303 Toyota indicates Cylinder 3 Misfire Detected.
Common causes
Common causes include Intake air leak, Faulty spark plug #3, Faulty ignition coil #3.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
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Code Popularity 118,317
How popular is this code, among other codes? Medium
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Table of contents Created and updated by William Orellana on Aug 25, 2022
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Code P0303 Toyota Description

When the engine misfires, high concentrations of Hydrocarbons (HC) enter the exhaust gas. Extremely high hydrocarbon concentration levels can cause an increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the Engine Control Module (ECM) monitors the misfire count. When the temperature of the three-way catalytic converter reaches the point of thermal degradation, the ECM blinks the MIL. To monitor misfires, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels and could cause emission control system performance deterioration, the ECM illuminates the MIL and stores a Diagnostic Trouble Code (DTC).
OBDII Code P0303 Toyota - Cylinder 3 Misfire Detected - AutoCodes.com
P0303 Toyota Code - Cylinder 3 Misfire Detected
What does this mean?

What are the Possible Causes of the DTC P0303 Toyota?

  • Intake air leak
  • Faulty spark plug #3
  • Faulty ignition coil #3
  • Clogged or faulty fuel injector #3
  • Fuel injectors #3 harness is open or shorted
  • Fuel Injectors #3 circuit poor electrical connection
  • Ignition coils #3 harness is open or shorted
  • Ignition coils #3 circuit poor electrical connection
  • Incorrect Fuel pressure
  • Faulty Mass Air Flow (MAF) Sensor
  • Faulty Engine Control Module (ECM)
  • Faulty Engine Coolant Temperature (ECT) Sensor

How to Fix the DTC P0303 Toyota?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

The P0303 code means that cylinder #3 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder #3. If the problem persists more tests need to be done to diagnose the problem. See "Possible Causes" for the most common problems.





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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0303 Toyota code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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Information for Specific Toyota Models

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0303 Toyota Code

1. What are common symptoms of OBDII code P0303 in a Toyota indicating a cylinder 3 misfire?

Symptoms may include engine rough idle, loss of power, poor acceleration, and noticeable vibrations while driving.

2. What are some possible causes of a cylinder 3 misfire in a Toyota triggering code P0303?

Common causes include faulty spark plugs, ignition coil issues, vacuum leaks, fuel delivery problems, and potential issues with the engine's compression.

3. How can I diagnose the specific cause of a cylinder 3 misfire in my Toyota triggering code P0303?

Diagnosis typically involves inspecting spark plugs, checking ignition coils, testing fuel injectors, examining vacuum lines, and conducting a compression test on the engine.

4. Can a dirty or clogged fuel injector cause a cylinder 3 misfire in a Toyota with code P0303?

Yes, a dirty or clogged fuel injector can disrupt the fuel delivery to cylinder 3, leading to a misfire and triggering OBDII code P0303.

5. Are there any DIY repair tips for addressing a cylinder 3 misfire in a Toyota with code P0303?

DIY repair tips may include replacing spark plugs, swapping ignition coils, cleaning or replacing fuel injectors, checking for vacuum leaks, and ensuring proper engine compression.

6. Is it safe to drive my Toyota with OBDII code P0303 indicating a cylinder 3 misfire?

It is not recommended to drive your Toyota with a cylinder misfire as it can lead to further damage to the engine and other components. Immediate attention and repair are advisable.

7. How much does it typically cost to repair a cylinder 3 misfire in a Toyota with OBDII code P0303?

The cost of repair can vary depending on the specific cause of the misfire, but it may range from a few hundred dollars for basic fixes to over a thousand dollars for complex issues.

8. Can a cylinder 3 misfire in a Toyota triggering code P0303 be caused by a faulty ignition coil?

Yes, a faulty ignition coil for cylinder 3 can lead to a misfire and trigger OBDII code P0303. It's advisable to check and potentially replace the ignition coil if necessary.

9. Will resetting the OBDII system clear the P0303 code for a cylinder 3 misfire in my Toyota?

Resetting the system may temporarily clear the code, but if the underlying issue causing the misfire is not addressed, the code is likely to reappear. It's crucial to diagnose and fix the root cause.

10. Can extreme weather conditions impact the occurrence of a cylinder 3 misfire in a Toyota with code P0303?

Extreme weather conditions, such as very cold or hot temperatures, can sometimes exacerbate existing issues that lead to a misfire, so it's essential to ensure your vehicle is well maintained and prepared for varying weather conditions.

Discuss the causes and fixes for P0303 Toyota OBDII Code

Submit a New Comment

  • An easy test when one cylinder misfires is to swap the ignition coil unit between the misfiring cylinder and a working cylinder. If the error follows the ignition coil unit, it is faulty.

    Reply to Comment

  • Thanks. Good advice.

    Reply to Comment

  • Hi
    Have a 2002 Toyota 2wd/4cyl Tacoma Prerunner

    First I had a p0300.. Installed NEW plugs..still p0300...switched #3 & #1 coils
    then had a p0303 test AFTER switching the #3 coil with the #1..so coil #3 was now in the #1 position and seems to be ok. Reading is stillp0303
    Had a Leak down & compression test for P0303 ...here are the readings
    Cylinder #3 compression 110PSI. Cylynder #1 compression 135PSI, Cylinder #3 leakdown failed 85% for intake valve
    I am now told I need a valve job,(850.00 to 1250.00) but up above in THIS article it lists other things BUT NOT valves.
    Also we had Bosch (good ones) plugs put in, by not the same mechanic. Now I'm told they are NOT the best for Japanese trucks. Are NGK or Denso the best or is Bosch OK?

    PLEASE help as I am an older single woman who needs some advice.

    Thanks in advance

    Reply to Comment

  • This was really helpful I did it on my truck and it helped thankfully it was just the spark plug and the coil so they were easy to repair.

    Reply to Comment

  • Thank you, I'm glad was just the coil and spark plug!!

    Reply to Comment

  • i did the swap but the error stayed at cylinder 3..any solution

    Reply to Comment

  • Hi
    Have a 2014 Toyota camry

    First I had a p0300.. Installed NEW plugs..still p0300...switched #3 & #1 coils
    then had a p0303 test AFTER switching the #3 coil with the #1..so coil #3 was now in the #1 position and seems to be ok. Reading is stillp0303
    reading says cylinder 3 is misfiring.now it hard for engine to start

    Reply to Comment

  • The next step is to change or swap the spark plug. If the problem persist, then you may have to replace the fuel injector.

    Reply to Comment
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