What's the 7e8 and 7e9 engine code mercedes?

If You're getting codes $7E8 and $7E9 on Your Mercedes-Benz vehicle, then You're in for a world of trouble! Just kidding, actually You're not. Those aren't codes at all -- they're actually placeholders for when Your scan tool is unable to decipher the information its receiving over the diagnostic port. In essence, it's telling You that there's a code there, but that it's incapable of translating the information that it's being given into a readable (and diagnosable) code. I'd recommend gaining access to another scan tool -- perhaps a better one. Many auto parts stores will perform this service for free. With more information, You'll actually be able to translate this into a meaningful diagnosis. However, as it stands, all You know is that You have trouble codes -- not what they are.