Ok, maybe I'm over thinking it, I assumed Baro readings needed temp readings to adjust for pressure variance since the 2 are directly related to be accurate(temp effects pressure as does the altimeter for accurate Baro readings, and so would opening a window driving down the highway so perhaps a mute point again), and inside the cab would effect temp thus the need for outside temp for a FMU that doesn't display outside temp, and since the temp pins are on the plug it needs that data and makes the adjustment accordingly on the circuit board in the FMU, thus the need for a temp sensor on a FMU that has no temp display, maybe I'm all wet and over thinking it, so I just ordered the Hilux Temp sensor 83482-35010 so I have it, otherwise with no temp display what else is it needed for on this FMU. This FMU has no temp display like all the single sunroof button FMU's AFAIK, which makes sense because they went to the digital climate control with the outside temp display in it. I'll let everyone know how the install goes when I get it in my hands and all tied up. This later version FMU is a perfect match for a 99LTD basically in everyway, colour, fit, sunroof function and plug.