Still can't believe you got a '94 E320 for $200. Somebody must have thought it was toast. Flood car?
You need to try and pull the codes somehow. Be sure you are doing it right - hold 2-3 secs to initiate the blinks, count the blinks, do it again. When the number of blinks repeat, you are finished pulling codes. Hold the button 10 seconds to clear the codes(I think).
I have a DTC list for my m103 that I got here or some other Benz forum. Had the whole PDF (it's from a Baum Tools DTC manual) and it included the m104 DTCs, but can't seem to find it.
What does the wiring harness look like? It can cause all kinds of problems if it has deteriorated.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)