Toyota has a TSB on these for corrosion in the pins and plug/harness on the driver's side of the transmission. If you live where road salt is used it's likely going to be a problem at some point. The female portion of the plug faces up so it can hold water. And it's a total PITA to diagnose and an even bigger one to fix. Toyota sells a repair kit that includes the valve body wire harness and the female plug. It does require dropping the pan to install. The male side of the plug isn't available though, and neither are the pins to repair it. Toyota wants you to buy an entire transmission wire harness to fix that side. I spent a number of hours on my back with a mirror over the plug trying to figure this one out on my 05 tacoma and finally brought it to a friends shop for them to fix it. Fortunately they got a donor plug from a 35k mile truck so they repaired my original harness. My truck spent it's first 5 winters in central Florida so lucky me my truck didn't have a problem until it had 140k on it well out of warranty. But apparently it's quite common here in New England. Pull that plug apart and pack it with dielectric grease before it's a problem!
