Long ago my team supported a database product. A customer called in with "Error 35". My guy looked up error codes in our manual: "You should never get error 35." I don't recall how much time it took Engineering to read the code to debug this. But seriously, somebody originally took the time to write the meaningless message into the manual.
Different story. My van threw an idiot-light "Check Engine" message on the dash. Well, that's not good, but I bought a maintenance contract, so to the dealer I go. Those bastards charged me $300 to read my OBD port and tell me my battery was low. You know, there is also a "Battery" idiot-light; why wasn't that one displayed instead? I went out and bought a FIXD device so now I can read my own error codes and save $300 the next time.