In my engine compartment, by the 2 oil pressure switches and the oil temp sensor.
The latter 3 are yellow, blu/blk/, and grn/blk. The blue/white just hangs there and leads back to the firewall and ecu.
Logic would dictate that it should plug into something within a 4 inch diameter circle from where it comes out of the black casing that protects all of the wires. But I can't find anything not plugged in.
I have the $100 VW book with wiring diagrams and all, but.... needle in haystack looking for 1 wire. I found all the oil sensors and switches, but no mention of the fourth item that would require a blu/wht.