Peugeot 5008 Torque Converter Failure

That sounds suspiciously like a classic torque converter failure. The symptoms you describe, combined with the error code, strongly point in that direction. Have you checked the transmission fluid level and condition? Low or burnt fluid can exacerbate these issues, though it's unlikely to be the root cause if the lock-up clutch is indeed failing.

Thanks for the quick reply! I did check the fluid, and it seemed okay, maybe a little dark but not burnt smelling. If it is the torque converter, is a full transmission rebuild necessary, or can just the converter be replaced? And what kind of costs am I looking at here?

While technically you can replace just the torque converter, it's generally considered best practice to inspect the entire transmission when you're already that deep inside. Debris from the failing converter can contaminate the valve body and other components, leading to future problems. Given the mileage on your 5008, a comprehensive inspection is warranted. At this point, I would strongly advise you to take your vehicle to a reputable workshop for a proper diagnosis and repair estimate.

You were spot on! Took it to a transmission specialist, and the torque converter lock-up clutch was indeed toast. They recommended a full transmission service and converter replacement, which set me back a hefty 2120€, but at least it's running smoothly again. Thanks for pointing me in the right direction!