"I did the Diagnostic Module and it gave me Code 17: data exchange malfunction between individual control modules..."

I keep reading stuff like that on here or "check your codes".... I see where there is a box in front of the battery, with orifices to penetrate with something...

What's used to read these codes? Is that what the OBD is all about? What can I look up in the archives to read more about it.?

I posted something similar the other day in ref to what tool to use to read OBD or OBD II (not sure which is my 95).

thanks

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1995 E320 smoke silver / parchment