DMax transmission oil pressure sensor issue

Sounds rough! Have you checked your gearbox oil level? Low oil pressure is a classic symptom. Is it shifting weird all the time, or only when the engine's hot? I had similar issues on my old Hilux, and it turned out the oil cooler lines were partially blocked, causing the oil to overheat and lose viscosity, which affected the pressure. But first, check that oil level!

Thanks for the quick reply! I thought about the oil level and had a quick look under the car, but it's hard to tell exactly what it is without getting right under it and maybe draining some. Is there a dipstick or something I'm missing? I'm pretty sure the problem is all the time, not just when it is hot. Where exactly were the oil cooler lines on your Hilux, and how did you spot the blockage?

No dipstick on those, I believe, you'll need to check the level plug on the transmission itself. If the oil level is fine, and the problem's there all the time, and with that sensor fault showing, it really does sound like either a faulty sensor or a genuine pressure issue. I'm thinking it would be best to have a workshop take a look at the pressure with a proper gauge before you start replacing parts. Could save you a lot of money and time!

Thanks so much for the advice! You were spot on about the oil level. Turns out it was critically low. Topped it up, but the light stayed on and the shifting was still rough, so I took it to the local garage. They confirmed it was the transmission oil pressure sensor and replaced it. Total cost was 365€, including the sensor and labour. Runs like a dream now. I really appreciate the pointers!