Q: 2008 Kia Sedona, 3.8L V-6, transverse : check engine light constant on; occasional random misfire(P0300) with P2198

If you are getting random misfire codes and O2 sensor codes after getting fuel i suggest you have a fuel sample test to see if there is excessive water in the fuel. You can try adding some drygas in the tank to try and disperse the water and run down to below 1/2 tank and refill at another gas station. You should never get fuel when you see a gas truck at the station or take a chance at getting excessive water in your fuel.

Bank 1 is the cylinder bank that has number one cylinder in it: usually the front bank on a V type engine. Sensor 1 is the upstream sensor in the exhaust manifold. But I don’t think you are having an O2 sensor problem. The P0154 doesn’t necessarily mean the sensor is bad, it just means that it is not sweeping. That could be due to a variety of causes. The first thing to check for in any drivability problem is air leaks. Any air that gets into the engine without being measured will lean out the system and cause problems. Look at all the rubber hoses and boots under the hood to be sure they are well connected and in good condition. However, your P2198 says that the rear bank is running rich. .This could be a fuel pressure regulator problem or a fuel injector that is leaking. I don’t think water in the fuel would give you this code. Still, it is always prudent to check the fuel for contamination before you spend too much time and money on diagnosis. IF you decide this is too much trouble to work out yourself, you can contact YourMechanic. They can send a technician to your home or office to check out your Kia and let you know what it is going to take