S40 Gear Shift Indicator Fault

Whoa, that sounds like a mess! Defective control unit is definitely a possibility. When you say 'error stored in the error memory,' do you know the specific error code? That could give us a better clue. Also, have you checked the basics, like the transmission fluid level and condition? Low or dirty fluid can sometimes cause similar shifting problems. It might be a long shot, but it's worth ruling out before jumping to the conclusion of a faulty control unit. Does it happen when the engine is cold or when it is hot, or both?

Thanks for the swift response. I don't recall the exact error code right now, but I can retrieve it. I inspected the transmission fluid recently, and the level appeared to be within range, but I did not assess its condition in detail. The symptoms seem to be present regardless of whether the engine is cold or at operating temperature. Could you elaborate on how the error code might point to a more specific cause? Could the instrument panel be the culprit?

Okay, so the fluid level is good, and the temperature doesn't seem to matter. That does point away from simple fluid issues. Given the range of symptoms, especially the 'gear selection display in speedometer without function' along with the shifting problems and the stored error, I'd lean towards the 'affected control unit defective' being the right track. These symptoms do not point to the instrument panel as the source of the problem. Sadly, that likely means a trip to a trusted workshop is in order. Those control units can be tricky to diagnose and even trickier to replace yourself without the right tools and software. Be prepared for a bill around 1000€.

I appreciate your insights and guidance. Your assessment confirms my suspicions regarding the control unit. I will proceed with taking the vehicle to a reputable workshop for further diagnosis and repair. I can report back, if you wish.