2003 BMW X5 4.6IS with P0491 Code
 

Hello. This is my first post here. I hope I could get some help in regards to my issue. I have 2003 X5 4.6IS. It is been getting the P0491 code. I already went through all that can be read about the P0491 and P0492 codes. Everyone that gets the both codes at the same time can isolate the problem with the Air pump or the valve. My issue is that I'm getting ONLY P0491 which is for bank one. Already checked the pump,valve all vacuum lines, and cleaned the metal tube line that goes from the valve to the heads. It was full with carbon. I'm starting to think that the car does have the carbon build up in the passenger head. The strange thing is that i have no hesitation issues or cold start problems or any smoke what so ever. The car runs fine with no problems at all. Could the problem be in the Bank 1 Sensor 1 O2? Can the carbon build up issue be possible to resolve with a software? Any help, suggestion and information will be greatly appreciated.

It is an uncommon but not unheard of problem. I lucked out with cleaning the crossover tube, but there have been a few instances of carbon build-up in the passages that the air flows through, and the only way to fix it is to pull off the head and clean it. You could try seafoaming it or getting something in there to clean it out, but I don't know how well it'll work.

What and how would be the best way to seafoam the air passages?

No idea, never tried it.

anyone?