It sounds like you got the cover off, but you did not pull the tach sending unit out. Pull on the piece that is under the cover. once you pull it off you will see the pin connections.

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2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
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'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
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'82 300D Turbodiesel - sold