Mercedes Viano System Readiness Error

Sounds familiar! I had a similar issue with my Vito, though I can't recall the exact year of manufacture. I also did an OBD2 read, and then the system readiness wouldn't complete. Have you tried driving it for a while? Some say that the system needs a drive cycle to reset after a computer reset from the OBD2 tool.

Yes, I've driven it quite a bit since the OBD2 read – probably around 200 km. I've tried different driving styles too, thinking maybe a specific cycle would trigger it. Still no luck. Did yours eventually clear itself, or did you have to do something specific?

No, mine didn't clear itself unfortunately. After a good while of trying, I ended up taking it to a workshop. They told me that sometimes these systems can get a bit finicky after an OBD2 intervention, especially if there were any interruptions during the process. They ran a full diagnostic and cleared everything. They suspected something went wrong during the computer reset.

That's exactly what I needed to hear. I was dreading a costly repair. I took it to my local mechanic, explained the situation, and they reset the system readiness monitors. Passed the emissions test and it cost me 0€! You saved me a ton of stress and potentially a lot of money.