I got this error code a few days ago after a long run. I did notice that the exhaust under the engine appears to be in quite bad shape when I did the oil change.

Here's a video of it running. It sounds far worse on video than in real life. It's quite a faint repetitive sound in person. Just an exhaust leak do you think..?

 

Blown gaskets. I'd expect you'd be able to see exhaust exiting around the wheel on cold days.

 

Cheers! I was worried it was a bottom end noise but it's not very crunchy like it sounds in the video.