I don't think disconnecting the battery will clear the codes. You will need to look at JimF's web page...
http://pages.prodigy.net/jforgione/MB_X11.html
and build the home brew blinker box. This tool is invaluable when trouble shooting the systems in this car. A manual with all the codes can be bought from JimF as well. Alternately, a subscription to Alldata will also have all the codes, as well as all the wiring diagrams (and more) for this car. If you do decide to purchase a subscription to Alldata, may I ask that you use the Alldata link on my website? I get a small commission that way. I have found Alldata extremely useful, it has everything I've needed for my 95 S600. I still think you should check the wiring of the MAF and the ETA too.