Skip the auto shop - Our mechanics make house calls

P0309 OBD-II Trouble Code: Cylinder 9 Misfire Detected

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...


Related questions

Q: I accidentally drove through 2 feet of water, I have replaced several parts but the car still runs poorly

You did not mention replacing the air filter after it got wet. The engine and its sensors were not designed to go through water and will get damaged. You may have also damaged internal engine parts like bending engine piston...

Q: I have questions about my 2009 kia spectra's CEL and the codes I had read. Car run's good and was running good when light came on.

Given the three codes, a known issue with sensor wiring in that vehicle (to be discussed momentarily), and only 89,000 miles on the engine, I would judge the likelihood of sensor failure to be "average". That is, there are lots...

Q: When I accelerate it has no power. It only goes slowly. I have a code PO700 that has came up.

Hello. Code P0700 is the trouble code for an issue with the vehicle's transmission control system. If the computer detects an issue within the transmission control system it will set off the Check Engine Light in order to alert the...