p1550 error code just once

[obsession01]

I have a 1995 Eurovan Syncro with an AHU 1.9 conversion. Van sat for 4 days at ski area and when I headed down the hill it went into limp mode. I have a Scan II gauge and got a p1550 error code. I shut the van off and reset code. All is good after restart and now 10 days later no problems. Curious about this. Motor has 4000 miles after total rebuild with Stage II cam, hybrid turbo, and big injectors.
Paul

[chittychittybangbang]

Could be related to altitude and loose hose or bad valve. p1550 is n75.