Those transmissions are well known for an O-ring leakage at the connector, soaking the connector plug in fluid. This will cause the faulty conductor plate code. I would pull the plug to see if it is wet with fluid before doing any more shot-in-the-dark repairs. During routine fluid replacement, this O-ring should be replaced.

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'96 C280 (gone)
'97 C36
'05 C230k