Another data point to add. After the CEL coming back on 6 days ago the light went off by itself today. I'm guessing that the ambient temps are back up and the SAI system is not being used/checked. I still plan to use the guidance provided and check it out when I get the chance...and it's not 120 degrees in my garage....

I had these codes come on the other day. Was caused by one of the vacuum lines coming off. Probably from me moving something. From the diagram from member Thom#### (sorry couldn't remember the numbers) it was where line 27 connects to 'Y' shaped item 21. After that was reattached and codes cleared they have not come back.

I have the same code plus P0410. The air change over valve was not holding vacuum so replaced it with a new one from the dealer. It was a PIA to get out from the top but got it all done w/o taking anything else out. Will drive the car & see if the codes re-appear. Also got the P1691 CEL malfunction, bulb was out so replaced that too.