OK so, with info from two similar threads, I ran my 1995 C280 whcih had the same
PO441 check engine light code, up to normal temp and the valve did not feel active.
I removed the valve, easy enough, and sprayed liberal amounts of WD40 into both inlets. Only one side will take up most of the liquid. Turned the valve upside down and let it sit for about 10 min. Then I tested momentarily with a 12 volt source. It did click so I was satisfied that it worked electrically.
Before reinstalling, I sprayed in more wd40 and let it sit upsidedown for some more.
Removed excess and shook it around. Installed it.
The engine was already close to operating temp when I removed the valve. At first I felt nothing overt and was trying to decipher whether the slight illusion of a frequent vibration was the valve or the chassis.
As I was about to measure the harness socket with a test lamp, the valve began to really thump like a "heart beat". It is very palpable, not a sublime sensation.

So, now I have the battery disconnected to reset the CEL light and hope for the best.

At least I know that the valve is easy to remove in the event that I have to relace it later with a new one from FastLane.

Thanks to this forum's members!!

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD