Just picked up a CD player for a friends '99 ML320. It goes to the inserted CD, displays "Loading" and then gives an error 1 message.
It is the proper Matsu****a (Panasonic) that was installed in the '98 and '99 models.

Anyone know what this error indicates on these units?

Found the answer.

Error 1 indicates a dirty disc. If it would have been error 2 then means disc is scratched.

The discs that I tried were not dirty so maybe I'll try cleaning the laser lens.

I see the manufacturer name got censored in my original post!