how to read the codes on 1994 Mercedes-Benz E320

it has the lite in the engine compartment

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1 answer
I know that this response is late for the original poster, but wanted to provide an answer for any others who are curious about this topic.

As was mentioned, the 1994 e320 has a built-in diagnostic LED. The best example of how to utilize it that I have seen is at:
http://youtu.be/HCcmL8hLcDY

This YouTube poster (eallevato) has a lot of detailed information for DIY-ers on this year and model, so it is worthwhile the check out the other videos he has uploaded.