Disco 2 Airbox Sensor - MHK100600 or MHK100820 ?

So, in my constant quest to find issues with my Disco, I've discovered (no pun intended) that the sensor on the side of my airbox, the AAP I believe, is part number MHK100600 according to

http://allbrit.de/UNI.cfm?PAGE=818743&SPRACHE=EN#10

Mine is an MHK100820 which only has three pins, but the plug has four, what's going on here?

Judging by the picture on the allbrit site and matching it with Google pictures, it does look like the 100600 AAP is the correct part. the Google picture shows it as having 3 pins.
The 100820 seems to be a totally different part judging by the picture and has 4 pins.
How many sockets do you have in the matching connector for the AAP?

MHK100600



MHK100820

It depends on the engine type, if it's 10P(Eu2) the 3 pin AAP is needed and if it's 15P(or beyond, Eu3) the 4 pin sensor is suitable cos that management need the ambient temp input too though if the vehicle's wiring has the 4 pin plug then the 4 pin sensor is needed and maybe somebody fitted the wrong one

OK, so what's happened here is that I'd focused too long on a picture of the 100600 and had convinced myself that the 100820 fitted to my airbox also had just three pins. I've just re-checked mine, and it does in fact have four....
Thanks for that explanation Sierrafery.