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P0306 Lexus Code - Cylinder 6 Misfire Detected

Quick Answer

When a Lexus diagnostic code P0306 is triggered, it indicates that a misfire has been detected in cylinder 6 of the engine. Common causes include Faulty spark plug: A worn-out or damaged spark plug can cause a misfire in the cylinder, Clogged fuel injector: A fuel injector that is clogged or not functioning properly can disrupt fuel delivery, Vacuum leaks: Leaks in the vacuum system can affect the air-fuel mixture. 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
P0306 Lexus indicates Cylinder 6 Misfire Detected.
Common causes
Common causes include Faulty spark plug: A worn-out or damaged spark plug can cause a misfire in the cylinder, Clogged fuel injector: A fuel injector that is clogged or not functioning properly can disrupt fuel delivery, Vacuum leaks: Leaks in the vacuum system can affect the air-fuel mixture.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P0306 Lexus Description

When a Lexus diagnostic code P0306 is triggered, it indicates that a misfire has been detected in cylinder 6 of the engine. This means that the fuel-air mixture in that specific cylinder did not ignite properly, resulting in a disruption of the combustion process. This can lead to a decrease in engine performance, reduced fuel efficiency, and potential damage to the catalytic converter over time.

OBDII Code P0306 Lexus - Cylinder 6 Misfire Detected
P0306 Lexus Code - Cylinder 6 Misfire Detected

Common Causes of P0306 Lexus

  1. Faulty spark plug: A worn-out or damaged spark plug can cause a misfire in the cylinder.
  2. Clogged fuel injector: A fuel injector that is clogged or not functioning properly can disrupt fuel delivery.
  3. Vacuum leaks: Leaks in the vacuum system can affect the air-fuel mixture.
  4. Low compression: Issues such as worn piston rings or valve problems can lead to low compression in the cylinder.
  5. Ignition system problems: Faulty ignition coils, wires, or modules can cause misfires in specific cylinders.

Symptoms of P0306 Lexus

  1. Rough idling: The engine may shake or vibrate excessively while idling.
  2. Loss of power: The vehicle may feel sluggish or struggle to accelerate.
  3. Increased fuel consumption: A misfire can lead to inefficient fuel combustion.
  4. Engine misfire: The engine may sound rough or hesitate during acceleration.
  5. Check Engine Light: The vehicle's onboard diagnostic system will trigger the Check Engine Light to alert the driver of a problem.

How to Fix P0306 Lexus

  1. Diagnostic check: Use a scan tool to identify the specific cylinder causing the misfire.
  2. Check spark plugs: Inspect and replace any faulty spark plugs in cylinder 6.
  3. Test fuel injector: Check the fuel injector in cylinder 6 for clogs or malfunctions.
  4. Compression test: Perform a compression test to check for any issues with cylinder compression.
  5. Ignition system check: Inspect the ignition coils, wires, and modules for any faults and replace as needed.

Cost to Fix P0306 Lexus

The cost of repairing a cylinder 6 misfire in a Lexus can vary depending on the specific cause of the issue and the parts needed for repair. On average, the cost can range from $100 to $500 for parts and labor. It's important to note that diagnostic time and labor rates can vary, so it's recommended to get quotes from local auto repair shops for a more accurate estimate.

What does this mean?

Tech Notes for P0306 Lexus

The P0306 code means that cylinder #6 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 #6. 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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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 P0306 Lexus Code

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  • 2003 LEXUS GS300, replaced plugs, plug wires, crank sensor, coils, igniter, throttle position sensor, cleaned throttle body, fresh gas, checked fuel injectors 13.3 to 13.5 all within range of one another. Hesitates to react when pressing accelerator, then kicks in to good RPM's.

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  • Looks like you have done almost everything. I recommend also checking the air filter and the Mass Air Flow (MAF) sensor. Replace filter and clean the MAF. Have you check the fuel pressure?

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  • I had checked the MAP. Pumped 8 gallons of old gas out through fuel pump under rear seat. Seem to pump out fairly fast. Observed when cutting and replacing coil connectors, very bad corrosion and cracked coating on wires.

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  • 2010 lexus LS 460 L. Just replaced all 8 direct injectors, wiring harness, both fuel pump gaskets and the intake gasket. Went to overtake a slow car this morning, car fell flat on its face. CE light and traction control light come on. Shut car off, turned back on, CE light and TC light off, went home and got spare car. Hooked up reader after work and this code was stored.

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    • Thanks for the detailed info. Since you just replaced all 8 injectors, wiring harness, and intake gaskets, and now you're getting a P0306 (misfire on cylinder 6), there’s a good chance something got disturbed or didn’t seat right during reassembly.

      Here’s what I’d check first:

      1. Ignition coil on cylinder 6 – It may have gotten damaged or not plugged in fully during the injector job. Try swapping coil 6 with another cylinder and see if the misfire follows.

      2. Fuel injector connection – Even though the injectors are new, double-check that the connector on injector 6 is fully seated and the wiring isn’t pinched or pulled.

      3. Intake manifold gasket or vacuum leak near cyl 6 – A small air leak at the intake runner for that cylinder could cause a misfire under load.

      4. Carbon buildup on valves – These engines are direct injection, and carbon buildup can cause random misfires—especially under load. Might be worth considering a cleaning if it keeps happening.

      5. Traction control light – That usually comes on with a misfire because the ECU cuts power or torque to protect the drivetrain. Not a separate issue.

      If it only happened once under hard acceleration and hasn’t returned, it might’ve been a one-off misfire due to a connector or loose part. But I’d still start by swapping the coil and checking the injector harness on #6 closely. Let me know if you want help finding #6—it’s rear passenger side.

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