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. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 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$20.00
Toyota$20.00
BMW$20.00
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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.

trouble codes
P0309
Check Engine Light

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Kevin

24 years of experience
388 reviews
Kevin
24 years of experience
Chevrolet Tracker - Check Engine Light is on - Stone Mountain, Georgia
Kevin was pretty cool! He explained things to me in a way I could understand and was able to offer me some good options to fix my car problems! Very professional and knew his stuff! Excellent experience

JOHNNY

33 years of experience
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JOHNNY
33 years of experience
Toyota Camry - Check Engine Light is on - Carmichael, California
Johnny was early, friendly, and thorough! He explained things to me about my car that I had no idea about before! I booked him for a diagnostic appointment and I’m definitely requesting him for a follow-up!

Benji

22 years of experience
184 reviews
Benji
22 years of experience
Jaguar XK - Check Engine Light is on - Phoenix, Arizona
Will absolutely recommend Benjie to all my friends, thorough and knowledgeable. Will have him back fit all future car repairs!

Marco

29 years of experience
124 reviews
Marco
29 years of experience
Kia Soul - Check Engine Light is on - Riverside, California
Marco was great. Cam on time, and explained everything he did. Also gave good recommendation for fixing as the problem has a Kia recall.


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