Code 34 is for a defective oxygen sensor -- the one on the left side just before the catalytic converter (G3/3). Code 45 is for a bad or missing signal from the left "CMP" sensor at the front of the left camshaft. If you want specifics for testing these, post back.

If you send me an email, V12, I can email you a manual for a Baum scan tool which includes the codes. Better still may be to get a copy of the R129 technical manuals on DVD. M-B sells it for $150, though there are illegal copies available for about $30.