FJCruiser Transmission Implausible Shifting

I have an FJCruiser as well, and I remember having similar transmission issues a while back. Did you check if your vehicle is experiencing undervoltage? My transmission went haywire like that, and it turned out the voltage regulator was failing, causing electrical gremlins that messed with the transmission control unit. Anything else unusual happening around the same time?

Interesting, I hadn't considered undervoltage. Besides the transmission issues, I haven't noticed anything else. How did you figure out that undervoltage was the cause of your transmission problems? Any other electrical issues that tipped you off?

Well, the issues started subtly. Dimming headlights, and the radio acting funny. Then the transmission started acting up. It’s hard to say exactly what gave it away other than coincidence. I'd suggest having it checked at a workshop nonetheless as it is quite difficult to measure the undervoltage without specific tools. Good luck!

Thanks, that's super helpful! I took it to a workshop, and you were spot on – it was indeed an undervoltage issue affecting the transmission. They replaced the voltage regulator, flushed the transmission fluid, and reset the system. Cost me about 240€, but the transmission is shifting smoothly again. Appreciate the insight!