P0309 OBD-II Trouble Code: Cylinder 9 Misfire Detected

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Cost of diagnosing the P0309 code

P0309 is a diagnostic trouble code (DTC) for "Cylinder 9 Misfire Detected". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$70.00$30.00
Toyota$70.00$30.00
BMW$70.00$30.00
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Check Engine Light

P0309 code definition

When the P0309 trouble code appears, it means that the powertrain control module has found a misfire from cylinder number 9.

What the P0309 code means

When this code appears, it means that the vehicle’s computer has found one of the engine cylinders is not firing properly.

What causes the P0309 code?

Potential causes of the trouble code:

  • Burned exhaust valve
  • Faulty catalytic converter
  • Poor compression
  • Running out of fuel
  • Faulty coil
  • Faulty oxygen sensor
  • Faulty fuel injector
  • Faulty wiring
  • Faulty spark plug
  • Defective onboard computer, although this is rare

What are the symptoms of the P0309 code?

There are a number of symptoms that could be caused by the P0309 code. In many cases, the service engine soon lamp will illuminate. In addition to the stored code, the vehicle may have a rough idle and the acceleration may feel choppy. The driver may also notice that there is a reduced amount of power in the vehicle. Some also find that the vehicle is more difficult to start.

How does a mechanic diagnose the P0309 code?

When the mechanic is trying to diagnose the P0309 code, he or she will attach their OBD-II scanner to the vehicle’s onboard computer. They will then scan for the code and any other codes that may be stored in the vehicle. At that point, they will reset the code and drive the vehicle to see if the codes return.

If the code returns, then they know it is a problem that they will need to fix. They will then start to look at all the other potential problems that could be causing the code to be stored, such as faulty fuel injectors, bad wiring, or a problematic catalytic converter.

Common mistakes when diagnosing the P0309 code

When this code presents itself, some mechanics may believe that the problem lies in the ignition system rather than other areas. While it is possible for the ignition system to be a fault, there are also other factors that could cause this misfire of the cylinder. It is important for the mechanics to look at all of the potential areas that could be causing problems and find the correct solution for the vehicle.

How serious is the P0309 code?

While the stored code and a service light that illuminates might not seem like a big problem, there are other potential issues with the P0309 code. Drivers who are in vehicles that do not accelerate properly when they are driving could be in danger. Any vehicle that is not performing properly has the potential to cause an accident. The best course of action is to take the vehicle to a mechanic who can diagnose it and make the proper repairs. This is true no matter what code has been stored.

What repairs can fix the P0309 code?

The following are some of the potential fixes that mechanics will attempt when trying to deal with the misfired cylinder number 9.

Additional comments for consideration regarding the P0309 code

The P0309 code, as with all trouble codes, is nothing to ignore. Take the vehicle to a mechanic to have it diagnosed and repaired properly as soon as possible.

Need help with a P0309 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

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Check Engine Light
P0309

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Kenneth

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17 years of experience
Have to say, Kenneth is everything mechanics need to strive for. He seemed extremely knowledgeable on all things car-related, is on-time and what I found the most important, is that he gave detailed recommendations on what steps to take first. I have an old, high-mileage, Navigator with multiple problems. In the interest of saving money and not just throwing parts at it hoping it'll run fine afterwards, he gave specific recommendations on what test to get first to make sure the internal engine is fine before tackling everything else wrong with the car. He schooled me on some car terminology which was helpful as well.
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Besty was very kind and patient. He was very honest with my questions.
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Good work! Quickly identified the issue (Fuel tank cap) and corrected it. Fair and honest, communicated well.
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Chris is very knowledgeable and explained the diagnostic readings in terms i could understand. Once i get the quote to fix my car i will decide if i want to have it fixed by Your Mechanic. If i decide to go ahead i would like Chris to be the Mechanic to fix my car!
2004 CHRYSLER SEBRING - CHECK ENGINE LIGHT IS ON - ORANGE, CALIFORNIA

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