Hey guys I'm new to the forum. I have an 04 545i with about 126,000 miles. I've had the P0492 error code for about a year now. I bought the car from a private dealership and they supposedly fixed it so I could pass smog. I passed smog, but a week later it came back on, and now a year later I still have the problem. I used seafoam to try and clear up what ever is clogging it. That worked for a week and came back on again. I'm running out of options since the shops I've been to want to charge ridiculous amounts of money. I've read that B-12 might work, and I'm looking in to buying the secondary air cleaner kit from AGA. My registration is up next month so anyone that can help me or give feedback I'd greatly appreciate it ASAP, thanks.

 

Remove your cabin air filters and check all vacuum lines connections at the rear of engine vonnected to the secondary air valves... the get old and brittle like all rubber on all bmw... then make sure all ccv lines and valves are in good shape... this is a good place to start without taking everything apart

 

V8s are notorious for having carbon buildup in the secondary air ports in the cylinder heads. Wouldn't be surprised if that's what your problem is.