Engine-CodesCadillac – P0306 Cadillac

P0306 Cadillac Code - Cylinder 6 Misfire Detected

Quick Answer

When the diagnostic trouble code P0306 appears on a Cadillac, it indicates that a misfire has been detected in cylinder 6 of the engine. Common causes include Faulty ignition coil in cylinder 6, Failing spark plug in cylinder 6, Clogged fuel injector in cylinder 6. 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 Cadillac indicates Cylinder 6 Misfire Detected.
Common causes
Common causes include Faulty ignition coil in cylinder 6, Failing spark plug in cylinder 6, Clogged fuel injector in cylinder 6.
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.
Table of contents Created and updated by William Orellana on Aug 30, 2024
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Code P0306 Cadillac Description

When the diagnostic trouble code P0306 appears on a Cadillac, it indicates that a misfire has been detected in cylinder 6 of the engine. A misfire occurs when the fuel-air mixture in the cylinder fails to ignite properly, resulting in a loss of power, rough idling, and potentially damaging the catalytic converter over time. This issue can lead to decreased fuel efficiency, increased emissions, and poor performance. The misfire can be caused by a variety of factors, including ignition system problems, fuel delivery issues, vacuum leaks, or mechanical issues within the engine.

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

Common Causes of P0306 Cadillac

  1. Faulty ignition coil in cylinder 6
  2. Failing spark plug in cylinder 6
  3. Clogged fuel injector in cylinder 6
  4. Vacuum leak in the intake manifold affecting cylinder 6
  5. Low compression in cylinder 6 due to issues with the piston rings or valves

Symptoms of P0306 Cadillac

  1. Rough idling or shaking while the vehicle is running
  2. Loss of power or acceleration
  3. Engine hesitation or stumbling during acceleration
  4. Check Engine Light illuminating on the dashboard
  5. Increased fuel consumption

How to Fix P0306 Cadillac

  1. Begin by diagnosing the specific cause of the misfire in cylinder 6 using a scan tool to identify the problem component.
  2. Replace the faulty ignition coil, spark plug, or fuel injector in cylinder 6 as needed.
  3. Check for any vacuum leaks in the intake manifold and repair them if found.
  4. Perform a compression test on cylinder 6 to determine if there are any internal engine issues causing the misfire.
  5. Clear the trouble code from the vehicle's computer and test drive the car to ensure that the misfire has been resolved.

Cost to Fix P0306 Cadillac

The cost of repairing a cylinder 6 misfire on a Cadillac can vary depending on the specific cause of the issue and the labor rates in your area. Generally, replacing a faulty ignition coil, spark plug, or fuel injector can cost between $100 to $300 each. Diagnostic time and labor rates at auto repair shops typically range from $80 to $150 per hour. Overall, the total repair cost for this issue can range from $200 to $800 or more, depending on the extent of the problem and the parts needed. It's recommended to consult with a professional mechanic to get an accurate estimate for your specific situation.

Tech Notes for P0306 Cadillac

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".

There is a Factory Service Bulletins for All 2000-2020 Cadillac Models:
2000-2020 Cadillac Factory Service Bulletin OBDII Code P0306
This Factory Service Bulletin explains how this condition may be caused by significant carbon build-up on the intake and/or exhaust valves due to fuel contamination or incomplete burning of the fuel.

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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.

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