Issue with downshifting manually in Sports Mode on AT

[Kat]

I have a 2012 GX with AT (and sports mode). Lately, if the weather is really warm or if I've been driving for a while, I can't downshift manually in sports mode which makes it frustrating when I have to use a lower gear on steep hills. Now, it does downshift automatically as I reduce the speed so there's no issues there and I can up-shift anytime I want to so I'm okay there. I've taken it to the dealership and saw it for themselves but they're a bit stumped. They're going to do some investigating and get back to me on my next visit there.

It started happening about a year ago but more so in the past few months. If it's cold, everything is fine. Once it reaches 5C, that's when I start having an issue.

I suspect there's an issue with a sensor of some sorts but am unsure. Did anyone else have a similar issue? If so, what was the problem and how did you fix it?

Thanks in advance!

[AwAfrican]

I mean you find just get a real manual transmission then you wouldn't have this issue......

Helpfulness: how is tranny fluid may be worth changing it...If it's a sensor issue replacing them could solve the issue otherwise there's no real way to tell

[TheMAN]

sounds like an electrical issue... could be wiring or switches
remember this: resistance increases as temperature increases