Has anyone out there ever had any speed sensor problems on their W124 E320?

I have a CEL with code 20, (speed signal not present) and a code 9 from pin 14 CC/ETA. I don't have any other codes that come back after clearing except these.

Arthur advised that I replace my brake stop switch, which I did. He also said that the speed sensor could be in the speedo unit. Isn't there also a sensor on one of the wheels?

I really don't want to replace the speedo if I don't have to. Any other suggestions?

Is this worth going to the dealer over?

Thanks,

Charles