Car won't shift past 3rd gear – transmission or just a sensor?

[barnabyquainton]

Driving my 2015 Nissan Pathfinder and suddenly it won't shift past third gear. The RPMs go up but the transmission just stays in third, no matter if I'm going 40 or 80 km/h. The check engine light came on at the same time. I limped home slowly but I'm terrified this is going to be a full transmission rebuild. A friend said it could be a simple speed sensor or a solenoid issue, not necessarily the whole gearbox. I really need a shop that has a good scanner that can read transmission codes properly, not just generic P0700 codes. I was looking at Top-Tier Repair Service Sharjah because someone in another thread said they're good with Nissan CVTs specifically. Has anyone taken a Pathfinder there for transmission problems? Do they actually diagnose or just say "replace the whole transmission" right away? I'm hoping it's something small but I want an honest opinion from a shop that knows these cars well. Also any idea what a transmission diagnostic fee usually runs? Would really appreciate any guidance before I tow it somewhere and get taken advantage of. Thanks.