While driving, the gearbox intermittently shifts gears on its own and often gets stuck in 3rd gear. I used a diagnostic tool, which flagged a fault with the "18D Gearbox input sensor circuit, 1. DEF = turbine speed faulty."
Despite searching Google and various forums, I haven't found a solution yet.
Additionally, the car sometimes jerks when switching gears, particularly when downshifting to first gear. On one occasion, it entered limp mode, and on rare occasions, it has attempted to start in 2nd or 3rd gear randomly.
I have attached a picture of the diagnostic. Any advice, please?
- 18D Gearbox input sensor circuit, 1. DEF = turbine speed faulty