If your 4Runner is 96-98, you will have to get an actual mechanical gauge. There is no transmission temp sent through the computer to the OBII port.
There have been a few people who buy a $40-50 gauge, and tap in to either the inbound or outbound tranny line.
If you have a 99+, there are tons of options. Scangauge II, apps on your phone with different adapters, etc.
motherfudruckers! I have a 1996, any suggestion on which mechanical gauge would you guys recommend?
Maybe fellow member Kball will post some pics of his. Simple but effective. If I had a pre 99 I'd use a similar set up.
I use an AEM Digital Trans/Water temp gauge. Comes with 4 faces plates. 2 for trans, 2 for temp. One is white, one is black.
That's pretty sweet. Is that coolant temp on the outside and trans temp on the readout?
It should be trans temp for both displays.