I have been fighting a 411 code since I got my truck back on the road nearly 2 years ago. I got a waiver of inspection for this to get my tag. It came up many times 35 miles after I reset the code and changed parts. Then I discovered Sea Foam and went 150 miles, then 350 miles, and came back on right before I went to reinspect. When I changed my radio about a month ago, the code reset and didn't come back on for 1000 miles. I had topped off my antifreeze because it was low and I think I have a bad head gasket.

My question: Would burning small amounts of antifreeze cause a sensor to send a signal and cause a code (like 411)? Can anything other than fuel in the system set it off?

A 411 is secondary air flow wrong direction, I think.

Thanks for any input.

 

Have you checked the check valve on your secondary air system?