Thanks. I know about temp corrections, especially the cold stuff. I thought FMS altitude data was supposed to be corrected for cold temp' so that you did not become dangerously low on path. But I've only flown VNAV/LNAV approaches with raw data backup and not the new fangled RNAV GNSS thingies.
It reminds a little of a mate, in his very old car some decades ago, who had an annoying low oil pressure light keep coming on. (no gauge) He kept checking the oil and it was full, so he disconnected the bulb. Engine seized due to broken oil pump. He had confused quantity with pressure. Duh! Now we would never do anything like that, would we? Remove the bulb, I mean.