Lexus LX diesel preheating lamp stays on

Sounds like you're on the right track. A persistent preheating lamp and a stored error code definitely point towards a glow plug issue. How's the engine starting, especially when it's cold? Any rough idling or excessive smoke?

Good question. Cold starts are definitely a little rougher than they used to be, and I've noticed a bit of a wobble at idle sometimes. Is it something I can fix myself or should I go to a workshop?

Okay, those symptoms pretty much confirm it. Given the symptoms and the error code, it's almost certainly a defective glow plug. While replacing glow plugs isn't rocket science, it can be tricky depending on their location and how seized they might be. If you're not super confident, I'd suggest taking it to a workshop to avoid snapping one off in the head. It'll probably cost around 440€ to get it sorted professionally.

Thanks for the advice! I appreciate the confirmation. I think I'll take it to a workshop. It's not worth the risk of making things worse. They'll sort it out. At least now I know what to expect cost-wise. Thanks again!